Acesulfame potassium compositions and processes for producing same

ABSTRACT

Compositions and processes for producing high purity acesulfame potassium are described. One process comprises the steps of providing a crude acesulfame potassium composition comprising acesulfame potassium and acetoacetamide, concentrating the crude acesulfame potassium composition to form a water stream and an intermediate acesulfame potassium composition comprising acesulfame potassium and less than 33 wppm acetoacetamide, and separating the intermediate acesulfame potassium composition to form the finished acesulfame potassium composition comprising acesulfame potassium and less than 33 wppm acetoacetamide. The concentrating step is conducted at a temperature below 90° C. and the separating step is conducted at a temperature at or below 35° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Application Ser. No.16/014,431 having a filing date of Jun. 21, 2018 which continuation ofU.S. application Ser. No. 15/704,386 having a filing date of Sep. 14,2017 (now U.S. Pat. No. 10,029,999), which claims priority to U.S.Provisional Patent Application No. 62/397,509, filed Sep. 21, 2016, thedisclosures of which are incorporated herein by reference in theirentirety.

FIELD OF INVENTION

The present invention relates generally to acesulfame potassium and toprocesses for producing acesulfame potassium. More specifically, thepresent invention relates to processes for producing high purityacesulfame potassium.

BACKGROUND OF THE INVENTION

Acesulfame potassium has an intense, sweet taste and has been used inmany food-related applications as a sweetener. In conventionalacesulfame potassium production processes, sulfamic acid and an amine,e.g., triethylamine, are reacted to form an amidosulfamic acid salt,such as a trialkyl ammonium amidosulfamic acid salt. The amidosulfamicacid salt is then reacted with diketene to form an acetoacetamide salt.The acetoacetamide salt may be cyclized, hydrolyzed, and neutralized toform acesulfame potassium. U.S. Pat. Nos. 5,744,010 and 9,024,016disclose exemplary acesulfame potassium production processes.

Typically, the acetoacetamide salt intermediate is cyclized by reactionwith sulfur trioxide in an inorganic or organic solvent to form a cyclicsulfur trioxide adduct. The solvent routinely utilized in this reactionis an organic solvent such as a halogenated, aliphatic hydrocarbonsolvent, for example, dichloromethane. The adduct formed by thisreaction is subsequently hydrolyzed and then neutralized with potassiumhydroxide to form acesulfame potassium.

Acesulfame potassium product and the intermediate compositions producedby conventional methods contain undesirable impurities, such asacetoacetamide (and acetoacetamide-N-sulfonic acid). Limits for thecontent of various impurities are often set by governmental regulationsor customer guidelines. Removal of many of these impurities usingstandard purification procedures such as evaporation, crystallization,and/or filtration has proven difficult, resulting in consumerdissatisfaction and the failure to meet standards.

The need exists for improved processes for producing high purityacesulfame potassium compositions in which the formation of impuritiessuch as acetoacetamide during synthesis is reduced or eliminated.

All of the references discussed herein are hereby incorporated byreference.

SUMMARY OF THE INVENTION

The application discloses processes for producing a finished acesulfamepotassium composition, the processes comprising the steps of: providinga crude acesulfame potassium composition comprising acesulfamepotassium, acetoacetamide and water, concentrating the crude acesulfamepotassium composition to form a water stream and an intermediateacesulfame potassium composition comprising acesulfame potassium andless than 33 wppm acetoacetamide (and optionally less than 33 wppmacetoacetamide-N-sulfonic acid), and separating the intermediateacesulfame potassium composition to form the finished acesulfamepotassium composition comprising acesulfame potassium and less than 33wppm acetoacetamide. The concentrating step is conducted at atemperature below 90° C., and the separating step is conducted at atemperature at or below 35° C. The weight percentage of acetoacetamidein the finished acesulfame potassium composition may be less than theweight percentage of acetoacetamide in the crude acesulfame potassiumcomposition. The intermediate acesulfame potassium composition maycomprise less than 33 wppm acetoacetamide-N-sulfonic acid. The providingof the crude acesulfame composition may comprise the steps of reactingsulfamic acid and an amine to form an amidosulfamic acid salt, reactingthe amidosulfamic acid salt and acetoacetylating agent to form anacetoacetamide salt, reacting the acetoacetamide salt with cyclizingagent in the cyclizing agent composition to form the cyclic sulfurtrioxide adduct, hydrolyzing the cyclic sulfur trioxide adduct to forman acesulfame-H composition comprising acesulfame-H, and neutralizingthe acesulfame-H in the acesulfame-H composition to form the crudeacesulfame potassium composition comprising acesulfame potassium andacetoacetamide. The concentrating step may comprise evaporating thecrude acesulfame potassium composition to form the water stream and theintermediate acesulfame potassium composition comprising acesulfamepotassium and less than 75 wt % water, and the evaporation residencetime may be less than 180 minutes. The separating may comprisecrystallizing the intermediate acesulfame potassium composition to formacesulfame potassium crystals and filtering the acesulfame potassiumcrystals to form the finished acesulfame potassium composition.Preferably, the concentrating comprises evaporating the crude acesulfamepotassium composition to form a water stream and an intermediateacesulfame potassium composition comprising acesulfame potassium andless than 50 wt % water, and the separating comprises crystallizing theintermediate acesulfame potassium composition to form acrystal-containing stream comprising acesulfame potassium crystals, andfiltering the crystal-containing stream to form the finished acesulfamepotassium composition. The filtering may be conducted at a temperatureat or below 35° C. and/or the crystallizing may be conducted at atemperature at or below 35° C. and/or may comprise at least twofiltration operations. In some cases, the evaporating may be conductedat a temperature below 85° C. and the intermediate acesulfame potassiumcomposition may comprise from 1 wppb to 33 wppm acetoacetamide (andoptionally less than 33 wppm acetoacetamide-N-sulfonic acid) and thefinished acesulfame potassium composition may comprise less than 33 wppmacetoacetamide. In one embodiment, the evaporating may be conducted at atemperature below 60° C. and the evaporator residence time is less than50 minutes and the intermediate acesulfame potassium composition maycomprise from 10 wppb to 25 wppm acetoacetamide (and optionally lessthan 30 wppm acetoacetamide-N-sulfonic acid) and the finished acesulfamepotassium composition may comprise from 10 wppb to 15 wppmacetoacetamide. In one embodiment, the evaporating may be conducted at atemperature below 46° C., the evaporator residence time may be less than30 minutes, the crystallizing may be conducted at a temperature below35° C., the intermediate acesulfame potassium composition may comprisefrom 10 wppb to 12 wppm acetoacetamide (and optionally less than 20 wppmacetoacetamide-N-sulfonic acid), and the finished acesulfame potassiumcomposition may comprise from 10 wppb to 7 wppm acetoacetamide. In somecases, the evaporating is conducted at a temperature ranging from 20° C.to 55° C.; the evaporator residence time ranges from 1 minute to 300minutes; the separating is conducted at a temperature ranging from −10°C. to 15° C.; the separating operation residence time ranges from 1 to180 minutes; the crude acesulfame potassium composition comprises from500 wppm to 2375 wppm acetoacetamide; the intermediate acesulfamepotassium composition comprises 10 wppb to 20 wppm acetoacetamide and 10wppb to 20 wppm acetoacetamide-N-sulfonic acid; and the finishedacesulfame potassium composition comprises from 10 wppb to 10 wppmacetoacetamide, and from 1 wppb to 20 wppm acetoacetamide-N-sulfonicacid. The crystallizing may be conducted at a pH below 10. The crudeacesulfame composition may further comprise solvent and wherein theprocess may further comprise removing solvent from the crude acesulfamepotassium composition prior to the evaporation. The processes maycomprise the step of separating from the acesulfame-H composition atransition phase comprising at least 2 wt % acetoacetamide to form apurified acesulfame-H composition, and the neutralizing may compriseneutralizing the acesulfame-H in the purified acesulfame-H compositionto form the crude acesulfame potassium composition comprising acesulfamepotassium and acetoacetamide. In one embodiment, the process comprisesthe steps of reacting sulfamic acid and triethylamine to form anamidosulfamic acid salt, reacting the amidosulfamic acid salt anddiketene to form acetoacetamide salt, contacting dichloromethane and asulfur trioxide to form a cyclizing agent composition, reacting theacetoacetamide salt with sulfur trioxide in the cyclizing agentcomposition to form a cyclic sulfur trioxide adduct, hydrolyzing thecyclic sulfur trioxide adduct to form an acesulfame-H composition,neutralizing the acesulfame-H to form the crude acesulfame potassiumcomposition comprising acesulfame potassium and acetoacetamide,evaporating the crude acesulfame potassium composition to form a waterstream and an intermediate acesulfame potassium composition comprisingacesulfame potassium and less than 75 wt % water, crystallizing theintermediate acesulfame potassium composition to form acesulfamepotassium crystals; and filtering the acesulfame potassium crystals toform the finished acesulfame potassium composition comprising acesulfamepotassium and less than 10 wppm acetoacetamide. The evaporating may beconducted at a temperature below 50° C., evaporator residence time maybe less than 30 minutes filtering may be conducted at a temperaturebelow 35° C., and/or crystallizing may be conducted at a temperaturebelow 35° C. The application also describes crude, intermediate, andfinished acesulfame potassium composition produced by the processesdescribed herein. In some cases, the application describes an acesulfamepotassium composition comprising acesulfame potassium and less than 33wppm, preferably less than 10 wppm acetoacetamide and optionally furthercomprises less than 33 wppm, preferably less than 10 wppmacetoacetamide-N-sulfonic acid. In some cases, the acesulfame potassiumcomposition further comprises 0.001 wppm to 5 wppm organic impuritiesand/or 0.001 wppm to 5 wppm of at least one heavy metal, e.g., the atleast one heavy metal being selected from the group consisting ofmercury, lead and mixtures thereof. In some cases, the acesulfamepotassium composition further comprises mercury present in an amount of1 wppb to 20 wppm and/or lead present in an amount of 1 wppb to 25 wppm.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to theappended drawing.

FIG. 1 is a process flow sheet of an acesulfame potassium productionprocess in accordance with one embodiment of the present invention.

FIG. 2 is a process flow sheet of an acesulfame potassium productionprocess employing one embodiment of a treatment scheme of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

Conventional processes for producing acesulfame potassium involvereacting sulfamic acid and an amine in the presence of acetic acid toform an amidosulfamic acid salt. The amidosulfamic acid salt is thenreacted with an acetoacetylating agent, e.g., diketene, to form anacetoacetamide salt. The acetoacetamide salt is reacted with a cyclizingagent, e.g., sulfur trioxide, to form a cyclic sulfur trioxide adduct.The cyclic sulfur trioxide adduct is then hydrolyzed and neutralized viaconventional means to form a crude acesulfame potassium compositioncomprising acesulfame potassium. This composition is phase separatedinto aqueous and organic phases. Most of the acesulfame potassiumseparates into the aqueous phase. As used herein, the term “crudeacesulfame potassium composition” refers to the initial product of theneutralization reaction or to the aqueous phase that is formed from thephase separation step (without any further purification). The crudeacesulfame potassium composition comprises at least 5 wt % acesulfamepotassium. The crude acesulfame potassium composition may be optionallytreated to form an “intermediate acesulfame potassium composition”and/or a “finished acesulfame potassium composition,” which arediscussed below.

Conventional acesulfame potassium compositions have been shown tocomprise several undesirable impurities, among them acetoacetamide andacetoacetamide salts, e.g., acetoacetamide-N-sulfonate triethylammoniumsalt. Acetoacetamide-N-sulfonic acid and salts thereof may also bepresent. Content limits for these compounds in the finished acesulfamepotassium composition are often determined by industry purity standardsand/or by standards established for particular end use products thatutilize acesulfame potassium as a sweetener. In some cases, limits forthese impurities are determined by governmental regulations. For mostapplications, high acesulfame potassium purity levels are preferred.Thus, crude acesulfame potassium compositions typically are treatedthrough various treatment operations to reduce the presence of theseimpurities. A non-limiting list of such treatment operations includes:evaporation, crystallization, and/or filtration.

Without being bound by theory, it has now been discovered that thesetreatment operations may create stress, e.g., thermal stress, onacesulfame potassium molecules. This thermal stress may also affectacesulfame-H, also known as sweetener acid, which is formed during thehydrolysis step and is a precursor to the acesulfame potassium. Thisstress on the acesulfame potassium and potentially on the acesulfame-Hcan result in degradation of these compounds, resulting in the formationof undesirable impurities. In some situations, this stress may cause theacesulfame potassium/acesulfame-H to degrade into its formation reactionreactants, e.g., acetoacetamide and/or salts thereof and/oracetoacetamide-N-sulfonic acid, which can lead to the formation ofadditional impurities.

It has also now been discovered that the use of specific treatmentparameters may advantageously reduce or eliminate stress on theacesulfame potassium (or acesulfame-H) and/or reduce or eliminateproduct degradation, which in turn reduces or eliminates the formationof additional impurities and ultimately leads to a high-purity endproduct.

In particular, conducting the treatment (or the individual treatmentsteps) within certain temperature ranges or limits and/or maintainingtreatment residence time within certain time ranges or limits now hasbeen found to surprisingly reduce or eliminate acesulfame potassium (oracesulfame-H) degradation and impurity formation, examples of whichinclude the (re)formation acetoacetamide and salts thereof.Traditionally, the treatment operations, e.g., evaporations, have beenconducted at higher temperatures so as to improve process speed and byrapidly removing water. The reduced degradation of acesulfame potassiumand acesulfame-H leads directly to the formation of the higher puritycrude acesulfame potassium compositions discussed herein, therebysimplifying subsequent treatment operations for forming the intermediateor finished acesulfame potassium compositions. The process alsoadvantageously leads to the formation of intermediate and finishedacesulfame potassium compositions having low acetoacetamide-N-sulfamicacid and/or acetoacetamide content.

Additional specific terms that are used herein are now defined.

“Acetoacetamide-N-sulfonic acid” as used herein, refers to the moleculeshown below. In some cases, acetoacetamide-N-sulfonic acid may be adegradation product of acesulfame potassium or acesulfame-H. The term“acetoacetamide-N-sulfonic acid,” as used herein, also includes salts ofacetoacetamide-N-sulfamic acid, e.g., potassium, sodium, and otheralkali metal salts.

“Acetoacetamide,” as used herein, refers to the following molecule:

Crude acesulfame compositions may be treated to form intermediateacesulfame potassium compositions and finished acesulfame compositions,and this treatment step may include one or more concentrating orseparating operations.

An “intermediate acesulfame potassium composition” refers to acomposition resulting from the concentrating of the crude acesulfamepotassium composition, e.g., the removal of water from the crudeacesulfame potassium composition. The intermediate acesulfame potassiumcomposition comprises at least 10 wt % acesulfame potassium, based onthe total weight of the intermediate acesulfame potassium composition,and has an acesulfame potassium weight percentage that is higher thanthat of the crude acesulfame potassium composition.

A “finished acesulfame potassium composition” refers to a composition(preferably directly) resulting from the separating, e.g., crystallizingand/or filtering, of the intermediate acesulfame potassium composition.The finished acesulfame potassium composition comprises at least 15 wt %acesulfame potassium, based on the total weight percentage of thefinished acesulfame potassium composition, and has an acesulfamepotassium weight percentage that is higher than that of the intermediateacesulfame potassium composition.

“Residence time,” as used herein, refers to the time period that acomposition (or stream) to be treated, e.g., a crude acesulfamepotassium composition, remains in a particular treatment operation.Residence time begins when the composition to be treated enters thetreatment operation, and residence time ends when the resultantcompositions (formed via the treatment) exit the treatment operation. Asone particular example, residence time for a concentrating operation,e.g., evaporation, refers to the time from when a crude acesulfamepotassium composition enters the evaporator until the intermediateacesulfame potassium composition exits the evaporator. As anotherexample, residence time for a separating operation, e.g.,crystallization, refers to the time from when a crude acesulfamepotassium composition enters the crystallizer until the intermediateacesulfame potassium composition exits the crystallizer.

The treatment of the crude acesulfame potassium composition may entailone or more operations, e.g., a concentrating operation and/or aseparating operation. Generally, a concentrating operation is notconsidered a separating operation. In some embodiments, theconcentrating operation(s) and the separating operation(s) make up theoverall treatment of the crude acesulfame potassium composition, whichresults in the finished acesulfame potassium composition. In some cases,the overall concentrating operation may include multiple individualconcentrating operations or units and the overall separating operationmay include multiple individual separating operations or units.

“Cyclization reaction time,” as used herein, refers to the time from thestart of the acetoacetamide salt feed to the termination of theacetoacetamide salt feed. In some cases, if indicated, the cyclizationreaction time may include additional time past the termination of theacetoacetamide salt feed, e.g., an extra 5 minutes or an extra minute.

“Wppm” and “wppb,” as used herein, mean weight parts per million orweight parts per billion, respectively, and are based on the totalweight of the entire respective composition, e.g., the total weight ofthe entire crude acesulfame potassium composition or the entire finishedacesulfame potassium composition.

Acesulfame Potassium Formation

Processes for producing high purity acesulfame potassium compositionsare described herein. In one embodiment, the process comprises the stepsof providing a crude acesulfame potassium composition comprisingacesulfame potassium and acetoacetamide (optionally present in an amountranging from 1 wppb to 50 wppm) and treating the crude acesulfamepotassium composition to form a finished acesulfame potassiumcomposition. The treatment may comprise concentrating the crudeacesulfame potassium composition to form a water stream and anintermediate acesulfame potassium composition comprising acesulfamepotassium and low amounts of acetoacetamide and then separating theintermediate acesulfame potassium composition to form the finishedacesulfame potassium composition comprising acesulfame potassium and lowamounts of acetoacetamide. As noted above, the crude acesulfamepotassium composition may be formed by reacting sulfamic acid and anamine to form an amidosulfamic acid salt and then reacting theamidosulfamic acid salt with an acetoacetylating agent to form anacetoacetamide salt. The acetoacetamide salt may then be cyclized,hydrolyzed, and neutralized (and optionally phase separated). Thesesteps are described in more detail below.

Importantly, in some embodiments, certain parameters of theconcentrating and/or the separating operations are maintained atparticular levels and/or within particular ranges. In some cases, thetemperatures at which the concentrating and/or the separating operationsare conducted are maintained at low levels. Also, in some embodiments,the residence times (of the crude acesulfame potassium composition inthe concentrating operation or of the intermediate acesulfame potassiumcomposition in the separating operation) are maintained at a low level.As a result, without being bound by theory, little or no additionalimpurities, e.g., acetoacetamide, are generated during treatment, e.g.,during the concentrating and/or separating operations, whichadvantageously provides for a more pure finished acesulfame potassiumcomposition. In some cases, the weight percentage of acetoacetamide inthe finished acesulfame potassium composition or in the intermediateacesulfame potassium composition is less than the weight percentage ofacetoacetamide in the crude acesulfame potassium composition, i.e.,acetoacetamide content is actually reduced during treatment.

In some embodiments, the concentrating operation, e.g., one or more ofthe steps that make up the concentrating operation, is conducted at ormaintained at a low temperature, e.g., a temperature below 90° C., e.g.,below 88° C., below 85° C., below 83° C., below 80° C., below 78° C.,below 75° C., below 73° C., below 70° C., below 65° C., below 55° C.,below 50° C., or below 46° C. In some cases, the temperature of theconcentrating operation may be maintained at a temperature above 0° C.,e.g., above 10° C., above 15° C., above 20° C., above 22° C., above 25°C., above 35° C., above 40° C. or above 50° C. In terms of ranges, thetemperature of the concentrating operation may range from 0° C. to 90°C., e.g., 25° C. to 90° C., from 55° C. to 90° C., from 10° C. to 88°C., from 10° C. to 85° C., from 75° C. to 88° C., from 80° C. to 88° C.,from 15° C. to 85° C., from 75° C. to 85° C., from 20° C. to 83° C.,from 20° C. to 80° C., from 22° C. to 78° C., from 25° C. to 75° C.,from 25° C. to 73° C., from 15° C. to 50° C., from 25° C. to 65° C.,from 22° C. to 50° C., from 20° C. to 55° C., from 25° C. to 70° C., orfrom 30° C. to 60° C.

In some embodiments, the separating operation, e.g., one or more of thesteps that make up the separating operation, is conducted at ormaintained at a low temperature, e.g., a temperature below 35° C., below30° C., below 25° C., below 20° C., below 15° C., below 10° C., below 8°C., below 6° C., below 5° C., or below 0° C. In some cases, thetemperature of the separating operation may be maintained at atemperature above −25° C., e.g., above −10° C., above 0° C., above 5°C., above 10° C., above 15° C., above 25° C., or above 30° C. In termsof ranges, the temperature of the separating operation may range from−25° C. to 35° C., e.g., −10° C. to 35° C., from 0° C. to 35° C., from5° C. to 30° C., from −10° C. to 30° C., from −10° C. to 25° C., from−10° C. to 20° C., from −10° C. to 15° C., from 0° C. to 25° C., or from−10° C. to 30° C. The employment of the aforementioned temperatures inthe treatment advantageously improves final product purity.

In some embodiments, the concentrating operation, e.g., one or more ofthe steps that make up the concentrating operation, is conducted at ormaintained at a low residence time. In one embodiment, residence time isless than 180 minutes, e.g., less than 170 minutes, less than 150minutes, less than 120 minutes, less than 100 minutes, less than 90minutes, less than 75 minutes, less than 50 minutes, less than 40minutes, less than 30 minutes, less than 20 minutes, or less than 10minutes. In terms of lower limits, residence time may be at least 1second, e.g., at least 10 seconds, at least 1 minute, at least 10minutes, or at least 15 minutes. In terms of ranges, the residence timemay range from 1 second to 180 minutes, e.g., from 10 seconds to 180minutes, from 1 minute to 180 minutes, from 10 minutes to 150 minutes,from 1 minute to 50 minutes, from 1 minute to 30 minutes, from 10minutes to 100 minutes, from 1 minute to 80 minutes, from 10 minutes to80 minutes, from 10 minutes to 50 minutes, from 15 minutes to 90minutes, or from 15 minutes to 75 minutes. The same residence timelimits and ranges are applicable to the separating operation, e.g., oneor more of the steps that make up the separating operation. Theemployment of residence times in the concentrating operation and/orseparating operation advantageously improves final product purity.

In some embodiments, the concentrating operation, e.g., one or more ofthe steps that make up a concentrating operation, is conducted at ormaintained at a low pH. In one embodiment, the pH of the separating ismaintained below 10.0, e.g., below 9.5, below 9.0, below 8.5, below 8.0,below 7.5, below 7.0, or below 6.5. In terms of ranges, the pH of theconcentrating operation is preferably maintained between 6.0 and 10.0,e.g., between 6.5 and 9.5, between 7.0 and 9.0, or between 7.5 and 8.5.The same pH limits and ranges are applicable to the separatingoperation, e.g., one or more of the steps that make up the separatingoperation. The employment of low pH levels in the concentratingoperation or separating operation advantageously improves final productpurity.

In cases where evaporation is utilized in the concentrating operation,the evaporation may be conducted at the aforementioned temperaturelimits and ranges. It has been discovered that, in addition to theaforementioned impurity reduction benefits, the utilization of lowerevaporation temperatures surprisingly limits or eliminates the formationof solids in the evaporator, e.g., solid acesulfame potassium, which canlead to safety issues, e.g., unnecessary pressure build-up or explosionof the evaporator.

The aforementioned parameter limits and ranges are applicable toindividual concentrating or separating operations that may make up theoverall concentrating or separating operation. For example, if theconcentrating operation may comprise evaporation, then the evaporationmay be conducted at a temperature below 90° C., e.g., below 88° C.,below 85° C., below 83° C., below 80° C., below 78° C., below 75° C.,below 73° C., below 70° C., below 65° C., below 55° C., below 50° C., orbelow 46° C. As another example, if the concentrating operation maycomprise evaporation, then the evaporation may be conducted at aresidence time less than 180 minutes, e.g., less than 170 minutes, lessthan 150 minutes, less than 120 minutes, less than 100 minutes, lessthan 90 minutes, less than 75 minutes, less than 50 minutes, less than40 minutes, less than 30 minutes, less than 20 minutes, or less than 10minutes. As another example, if the separating operation comprisescrystallization, then the crystallization may be conducted at a pH below10.0, e.g., below 9.5, below 9.0, below 8.5, below 8.0, below 7.5, below7.0, or below 6.5.

By performing the treatment under the temperature, pH, and/or residencetime parameters discussed herein, stress on the acesulfame potassiummolecules (in the crude acesulfame potassium composition) isadvantageously minimized during the separating operation. As a result,less acesulfame potassium degrades into the acetoacetamide during theseparating operation. Thus, the intermediate acesulfame potassiumproduct and the finished acesulfame potassium composition advantageouslycontain lower amounts of impurities, e.g., acetoacetamide (if any) thanwould typically form from acesulfame potassium degradation.

The concentrating operation, in some embodiments, comprises the step ofevaporating the crude acesulfame potassium composition to form a waterstream and an intermediate acesulfame potassium composition comprisingacesulfame potassium and less than 75 wt % water, e.g., less than 50 wt%, less than 40 wt %, less than 30 wt %, less than 20 wt %, less than 15wt %, less than 10 wt %, less than 50 wt %, less than 3 wt %, or lessthan 1 wt %. The water stream may refer to water that is evaporated fromthe crude acesulfame potassium composition, e.g., water that is notpresent in the intermediate acesulfame potassium composition. Theevaporating may be conducted at the concentrating operation parametersmentioned herein.

In some cases, the separating comprises the step of crystallizing theintermediate acesulfame potassium composition or a derivative thereof,to form the finished acesulfame potassium composition, which may be inthe form of acesulfame potassium crystals (or a composition/streamcomprising a the acesulfame potassium crystals). The intermediateacesulfame potassium composition may be a stream or a composition thatresults from the concentration of the crude acesulfame potassiumcomposition. The crystallizing may be conducted at the separatingoperation parameters mentioned herein.

In some embodiments the separating comprises the step of filtering theintermediate acesulfame potassium composition (or a crystal-containingderivative thereof) to form the finished acesulfame potassiumcomposition. A crystal-containing derivative of the intermediateacesulfame potassium composition may be a stream or a composition thatresults from the concentration of the crude acesulfame potassiumcomposition and that contains crystals either in dissolved or solidform. The filtering may be conducted at the separating operationparameters mentioned herein.

In preferred embodiments, the overall treatment comprises the steps ofevaporating the crude acesulfame potassium composition to form a waterstream and the intermediate acesulfame potassium composition comprisingacesulfame potassium and low amounts of water (see limits/ranges above),crystallizing the intermediate acesulfame potassium composition to formacesulfame potassium crystals, and filtering the acesulfame potassiumcrystals to form the finished acesulfame potassium composition.

In one embodiment, the process comprises the steps of providing thecrude acesulfame potassium composition comprising acesulfame potassiumand acetoacetamide and water and evaporating the crude acesulfamepotassium composition to form the water stream and the intermediateacesulfame potassium composition (as disclosed above). In thisembodiment, the residence time of the crude acesulfame potassiumcomposition in the evaporator is less than 180 minutes, e.g., less than170 minutes, less than 150 minutes, less than 120 minutes, less than 100minutes, less than 90 minutes, less than 75 minutes, less than 50minutes, less than 40 minutes, less than 30 minutes, less than 20minutes, or less than 10 minutes. In terms of ranges, the residence timemay range from 1 second to 180 minutes, e.g., from 10 seconds to 180minutes, from 1 minute to 180 minutes, from 10 minutes to 150 minutes,from 10 minutes to 100 minutes, from 10 minutes to 80 minutes, from 10minutes to 50 minutes, from 15 minutes to 90 minutes, or from 15 minutesto 75 minutes.

In some embodiments, the forming of the finished acesulfame potassiumcomposition from the intermediate acesulfame potassium compositioncomprises crystallizing the intermediate acesulfame potassiumcomposition to form acesulfame potassium crystals and filtering thecrystal-containing stream to form the finished acesulfame potassiumcomposition. In preferred embodiments, a falling film evaporator isemployed to form the intermediate acesulfame potassium composition.

The crude acesulfame composition may further comprise solvent, and insome embodiments, the concentrating operation comprises a solventremoval step, e.g., stripping solvent from the crude acesulfamepotassium composition, e.g., prior to concentrating (evaporating). Theprocess may comprise the steps of providing the crude acesulfamepotassium composition, stripping the crude acesulfame potassiumcomposition to form a solvent stream comprising solvent and a strippedacesulfame potassium composition comprising less than 50 wt % solvent,e.g., less than 40 wt %, less than 30 wt %, less than 20 wt %, less than15 wt %, less than 10 wt %, less than 50 wt %, less than 3 wt %, or lessthan 1 wt %, followed by the aforementioned concentrating operation andseparating operation. It has been found that removal of solvent, e.g.,methylene dichloride, surprisingly increases concentration efficiency.In addition to the stripping step, the separating operation may furthercomprise the evaporation, crystallization, and/or filtration steps.

In some embodiments, the separating operation comprises the step ofcrystallizing the intermediate acesulfame potassium composition to forma crystal-containing stream comprising acesulfame potassium crystals.The crystallization may be conducted at the pH ranges and limitsdiscussed above. The process may further comprise the step of formingfrom the crystal-containing stream the finished acesulfame potassiumcomposition. In some embodiments, the forming step comprises filteringthe crystal-containing stream to form the finished acesulfame potassiumcomposition. This embodiment may also utilize the aforementioned solventstripping step.

If filtration is employed in the separating operation, the filtration ispreferably conducted at the separating operation temperature limits andranges discussed herein. In cases where crystallization is utilized inthe separating operation, the crystallization may be conducted at thetemperature limits and ranges discussed herein.

In addition to the temperature limits and ranges, the crystallizationmay be conducted at the pH limits and ranges discussed herein. Forexample, the crystallization may be conducted at a pH below 10.0, e.g.,below 9.5, below 9.0, below 8.5, below 8.0, below 7.5, below 7.0, orbelow 6.5. In addition to the benefits of reducing acetoacetamideformation, it has also been found that conducting the crystallizationalso improves separation of dimers that may form in side reaction. It ispostulated that the lower pH levels promote precipitation of dimers.Higher pH levels have been found to promote dimer solubility. Theprecipitation advantageously provides for more efficient separationthereof.

In addition to the temperature limits and ranges, the crystallizationmay be conducted at the residence time limits and ranges discussedherein.

In one embodiment, the provision of the crude acesulfame potassiumcomposition (which is subsequently concentrated and separated) comprisesthe steps of reacting sulfamic acid and an amine to form anamidosulfamic acid salt and reacting the amidosulfamic acid salt withthe acetoacetylating agent to form the acetoacetamide salt. Theacetoacetamide salt may then be reacted with a cyclizing agent,optionally in the presence of a solvent, to form the cyclic (sulfurtrioxide) adduct composition. In preferred embodiments, the provision ofthe crude acesulfame potassium composition further comprises the step ofhydrolyzing the cyclic sulfur trioxide adduct to form acesulfame-H, andneutralizing the acesulfame-H to form the crude acesulfame potassiumcomposition. In some embodiments, the neutralizing step comprisesreacting the acesulfame-H (optionally in the acesulfame-H composition)with a neutralizing agent to form the acesulfame potassium composition.The reacting may comprise contacting the acesulfame-H with theneutralizing agent. The acesulfame potassium composition comprisesacesulfame potassium and impurities. The formation of the cyclic sulfurtrioxide adduct may yield a cyclic sulfur trioxide adduct compositionthat comprises the cyclic sulfur trioxide adduct and additional reactionside products and impurities. Similarly, the formation of theacesulfame-H may yield an acesulfame-H composition that comprisesacesulfame-H and additional reaction side products and impurities.

The specific methods employed to implement the desired temperatureand/or residence time features may vary widely. With regard totemperature, heat exchange equipment, e.g., cooling equipment, may beemployed. Temperature maintenance methods are well known in the art.

With regard to residence time, the respective separation streams may becontrolled to maintain the residence times discussed herein using theappropriate valves, gauges, metering devices, and piping.

The acesulfame potassium composition formed via the process(es)described herein will be a high purity acesulfame potassium composition.For example, the acesulfame potassium composition may compriseacetoacetamide salts in the amounts discussed above.

Acesulfame Potassium Compositions

The crude acesulfame potassium composition is formed by hydrolyzing acyclic sulfur trioxide adduct to form an acesulfame-H composition andneutralizing the acesulfame-H in the acesulfame-H composition to formthe crude acesulfame potassium composition, as discussed herein. Theproduct of the neutralization step is phase separated into aqueous andorganic phases. The crude acesulfame potassium composition may beobtained from the aqueous phase (without any further purification). Thecrude acesulfame potassium composition comprises acesulfame potassiumand acetoacetamide, e.g., less than 2800 wppm acetoacetamide, e.g., lessthan 2700 wppm, less than 2600 wppm, less than 2500 wppm, less than 2400wppm, less than 2000 wppm, less than 1500 wppm, less than 1000 wppm,less than 500 wppm, or less than 100 wppm. In some cases the crudeacesulfame potassium composition is substantially free of acetoacetamide(undetectable), e.g., free of acetoacetamide. In terms of ranges, thecrude acesulfame potassium composition may comprise from 1 wppm to 2800wppm acetoacetamide, e.g., from 1 wppm to 2700 wppm, from 10 wppm to2700 wppm, from 20 wppm to 2500 wppm, from 100 wppm to 2500 wppm, from500 wppm to 2500 wppm, from 1500 to 2400 wppm, from 500 wppm to 2375wppm, from 600 wppm to 2000 wppm, from 900 to 1900 wppm, from 300 wppmto 1500 wppm, from 400 wppm to 1400 wppm, from 600 wppm to 1200 wppm orfrom 700 wppm to 1100 wppm.

The crude acesulfame potassium composition may further compriseacetoacetamide-N-sulfonic acid, which may be present in the amountsdiscussed above with respect to acetoacetamide.

The finished acesulfame potassium compositions, which are typicallysuitable for end consumer usage, are formed by treating the crudeacesulfame potassium composition to remove impurities, as discussedherein. This finished acesulfame potassium composition preferablycomprises a mixture of acesulfame potassium and less than 33 wppmacetoacetamide, e.g., less than 32 wppm, less than 30 wppm, less than 25wppm, less than 20 wppm, less than 15 wppm, less than 12 wppm, less than10 wppm, less than 7 wppm, less than 5 wppm, less than 3 wppm, less than1 wppm, less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm.In some cases the finished acesulfame potassium composition issubstantially free of acetoacetamide, e.g., free of acetoacetamide. Interms of ranges, the finished acesulfame potassium composition maycomprise from 1 wppb to 33 wppm acetoacetamide, e.g., from 10 wppb to 32wppm, from 10 wppb to 25 wppm, from 10 wppb to 15 wppm, from 10 wppb to12 wppm, from 10 wppb to 10 wppm, from 10 wppb to 7 wppm, from 10 wppbto 5 wppm, from 10 wppb to 3 wppm, from 100 wppb to 15 wppm, from 100wppb to 10 wppm, or from 100 wppb to 5 wppm.

The finished acesulfame potassium composition preferably comprisesacesulfame potassium and less than 33 wppm acetoacetamide-N-sulfonicacid, e.g., less than 32 wppm, less than 30 wppm, less than 25 wppm,less than 20 wppm, less than 15 wppm, less than 12 wppm, less than 10wppm, less than 7 wppm, less than 5 wppm, less than 3 wppm, less than 1wppm, less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm. Insome cases the finished acesulfame potassium composition issubstantially free of acetoacetamide-N-sulfonic acid, e.g., free ofacetoacetamide-N-sulfonic acid. In terms of ranges, the finishedacesulfame potassium composition may comprise from 1 wppb to 33 wppmacetoacetamide-N-sulfonic acid, e.g., from 10 wppb to 32 wppm, from 10wppb to 25 wppm, from 1 wppb to 22 wppm, from 10 wppb to 22 wppm, from 1wppb to 20 wppm, from 10 wppb to 20 wppm, from 10 wppb to 15 wppm, from10 wppb to 12 wppm, from 10 wppb to 10 wppm, from 10 wppb to 7 wppm,from 10 wppb to 5 wppm, from 10 wppb to 3 wppm, from 100 wppb to 15wppm, from 100 wppb to 10 wppm, or from 100 wppb to 5 wppm.

The acetoacetamide-N-sulfonic acid and/or the acetoacetamide content maybe measured in the crude, intermediate, or finished acesulfame potassiumcompositions via high performance liquid chromatography (HPLC) analysis,based on European Pharmacopoeia guidelines for thin layer chromatography(2017) and adapted for HPLC. A particular measurement scenario utilizesan LC Systems HPLC unit from Shimadzu having a CBM-20 Shimadzucontroller and being equipped with an IonPac NS1 ((5 μm) 150×4 mm)analytical column and an IonPac NG1 guard column (35×4.0 mm). A ShimadzuSPD-M20A photodiode array detector can be used for detection (at 270 nmand 280 nm wavelength). Analysis may be performed at 23° C. columntemperature. As a first eluent solution, an aqueous mixture of tetrabutyl ammonium hydrogen sulfate (3.4 g/L), acetonitrile (300 mL/L), andpotassium hydroxide (0.89 g/L) may be employed; as a second eluentsolution, an aqueous mixture of tetra butyl ammonium hydrogen sulfate(3.4 g/L) and potassium hydroxide (0.89 g/L) may be employed. Elutionmay be conducted in gradient mode according to the following secondeluent flow profile:

0 to 3 minutes: constant 80% (v/v)

3 to 6 minutes: linear reduction to 50% (v/v)

6 to 15 minutes: constant at 50% (v/v)

15 to 18 minutes: linear reduction to 0%

18 to 22 minutes: constant at 0%

22 to 24 minutes: linear increase to 80% (v/v)

24 to 35 minutes constant at 80% (v/v).

Overall flow rate of eluent may be approximately 1.2 mL/min. The datacollection and calculations may be performed using Lab Solution softwarefrom Shimadzu.

One or more intermediate acesulfame potassium compositions may beformed, e.g., during the concentrating operation, for example viaevaporation. The intermediate acesulfame potassium compositionpreferably comprises a mixture of acesulfame potassium and less than 33wppm acetoacetamide, e.g., less than 30 wppm, less than 25 wppm, lessthan 20 wppm, less than 15 wppm, less than 12 wppm, less than 10 wppm,less than 7 wppm, less than 5 wppm, less than 3 wppm, less than 1 wppm,less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm. In somecases the intermediate acesulfame potassium composition is free ofacetoacetamide, e.g., substantially free of acetoacetamide(undetectable). In terms of ranges, the intermediate acesulfamepotassium composition may comprise from 1 wppb to 33 wppmacetoacetamide, e.g., from 10 wppb to 30 wppm, from 10 wppb to 25 wppm,from 10 wppb to 15 wppm, from 10 wppb to 12 wppm, from 10 wppb to 10wppm, from 10 wppb to 7 wppm, from 10 wppb to 5 wppm, from 10 wppb to 3wppm, from 100 wppb to 15 wppm, from 100 wppb to 10 wppm, from 100 wppbto 5 wppm. The intermediate acesulfame potassium composition maycomprise a mixture of acesulfame potassium and acetoacetamide.

As noted above, the crude acesulfame potassium composition is formed bythe aforementioned reactions, hydrolysis, and neutralization. The crudeacesulfame potassium composition is concentrated to form theintermediate acesulfame composition, which is then separated to form thefinished acesulfame potassium composition, as discussed herein. Inpreferred embodiments, the temperature at which the concentratingoperation, e.g., the evaporation, is conducted is at or below 90° C.,e.g., below 88° C., below 85° C., below 83° C., below 80° C., below 78°C., below 75° C., below 73° C., below 70° C., below 65° C., below 55°C., below 50° C., or below 46° C. (optionally at a temperature rangingfrom 0° C. to 90° C., e.g., 25° C. to 90° C., from 55° C. to 90° C.,from 10° C. to 88° C., from 10° C. to 85° C., from 75° C. to 88° C.,from 80° C. to 88° C., from 15° C. to 85° C., from 75° C. to 85° C.,from 20° C. to 83° C., from 20° C. to 80° C., from 22° C. to 78° C.,from 25° C. to 75° C., from 25° C. to 73° C., from 15° C. to 50° C.,from 25° C. to 65° C., from 22° C. to 50° C., from 20° C. to 55° C.,from 25° C. to 70° C., or from 30° C. to 60° C.); the concentratingoperation utilizes a residence time less than 180 minutes, e.g., lessthan 170 minutes, less than 150 minutes, less than 120 minutes, lessthan 100 minutes, less than 90 minutes, less than 75 minutes, less than50 minutes, less than 40 minutes, less than 30 minutes, less than 20minutes, or less than 10 minutes (optionally utilizing a residence timeranging from 1 second to 180 minutes, e.g., from 10 seconds to 180minutes, from 1 minute to 180 minutes, from 10 minutes to 150 minutes,from 1 minute to 50 minutes, from 1 minute to 30 minutes, from 10minutes to 100 minutes, from 10 minutes to 80 minutes, from 10 minutesto 50 minutes, from 15 minutes to 90 minutes, or from 15 minutes to 75minutes); the temperature at which the separating operation, e.g., thecrystallization and/or filtration, is conducted is below 35° C., e.g.,below 30° C., below 25° C., below 20° C., below 15° C., below 10° C.,below 8° C., below 6° C., below 5° C., or below 0° C. (optionally at atemperature ranging from −25° C. to 35° C., e.g., −10° C. to 35° C.,from 0° C. to 35° C., from 5° C. to 30° C., from −10° C. to 30° C., from−10° C. to 25° C., from −10° C. to 20° C., from −10° C. to 15° C., from0° C. to 25° C., or from −10° C. to 30° C.); the separating operationutilizes a residence time less than 180 minutes, e.g., less than 170minutes, less than 150 minutes, less than 120 minutes, less than 100minutes, less than 90 minutes, less than 75 minutes, less than 50minutes, less than 40 minutes, less than 30 minutes, less than 20minutes, or less than 10 minutes (optionally utilizing a residence timeranging from 1 second to 180 minutes, e.g., from 10 seconds to 180minutes, from 1 minute to 180 minutes, from 10 minutes to 150 minutes,from 10 minutes to 100 minutes, from 1 minute to 80 minutes, from 10minutes to 80 minutes, from 10 minutes to 50 minutes, from 15 minutes to90 minutes, or from 15 minutes to 75 minutes); the crude acesulfamepotassium composition may comprise less than 2800 wppm acetoacetamide,e.g., less than 2700 wppm, less than 2600 wppm, less than 2500 wppm,less than 2400 wppm, less than 2000 wppm, less than 1500 wppm, less than1000 wppm, less than 500 wppm, or less than 100 wppm (optionally from 1wppm to 2800 wppm acetoacetamide, e.g., from 1 wppm to 2800 wppm, from10 wppm to 2700 wppm, from 20 wppm to 2500 wppm, from 100 wppm to 2500wppm, from 500 wppm to 2500 wppm, from 1500 to 2400 wppm, from 500 wppmto 2375 wppm, from 600 wppm to 2000 wppm, from 900 to 1900 wppm, from300 wppm to 1500 wppm, from 400 wppm to 1400 wppm, from 600 wppm to 1200wppm or from 700 wppm to 1100 wppm) (the crude acesulfame potassiumcomposition may comprise acetoacetamide-N-sulfonic acid in the sameamounts); the intermediate acesulfame potassium composition may compriseless than 33 wppm acetoacetamide, e.g., less than 32 wppm, less than 30wppm, less than 25 wppm, less than 20 wppm, less than 15 wppm, less than12 wppm, less than 10 wppm, less than 7 wppm, less than 5 wppm, lessthan 3 wppm, less than 1 wppm, less than 0.8 wppm, less than 0.5 wppm,or less than 0.3 wppm (optionally from 1 wppb to 33 wppm acetoacetamide,e.g., from 10 wppb to 32 wppm, from 10 wppb to 25 wppm, from 10 wppb to15 wppm, from 10 wppb to 12 wppm, from 10 wppb to 10 wppm, from 10 wppbto 7 wppm, from 10 wppb to 5 wppm, from 10 wppb to 3 wppm, from 100 wppbto 15 wppm, from 100 wppb to 10 wppm, from 100 wppb to 5 wppm) (theintermediate acesulfame potassium composition may compriseacetoacetamide-N-sulfonic acid in the same amounts); and the finishedacesulfame potassium composition may comprise less than 33 wppmacetoacetamide, e.g., less than 32 wppm, less than 30 wppm, less than 25wppm, less than 20 wppm, less than 15 wppm, less than 12 wppm, less than10 wppm, less than 7 wppm, less than 5 wppm, less than 3 wppm, less than1 wppm, less than 0.8 wppm, less than 0.5 wppm, or less than 0.3 wppm(optionally from 1 wppb to 33 wppm acetoacetamide, e.g., from 10 wppb to32 wppm, from 10 wppb to 25 wppm, from 10 wppb to 15 wppm, from 10 wppbto 12 wppm, from 10 wppb to 10 wppm, from 10 wppb to 7 wppm, from 10wppb to 5 wppm, from 10 wppb to 3 wppm, from 100 wppb to 15 wppm, from100 wppb to 10 wppm, from 100 wppb to 5 wppm) (the finished acesulfamepotassium composition may comprise acetoacetamide-N-sulfonic acid in thesame amounts).

In a particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature below 85° C., theintermediate acesulfame potassium composition comprises from 1 wppb to33 wppm acetoacetamide (and optionally less than 33 wppmacetoacetamide-N-sulfonic acid), and the finished acesulfame potassiumcomposition comprises less than 33 wppm acetoacetamide (and optionallyless than 33 wppm acetoacetamide-N-sulfonic acid).

In another particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature below 60° C., the evaporatorresidence time is less than 50 minutes and the intermediate acesulfamepotassium composition comprises from 10 wppb to 25 wppm acetoacetamide(and optionally less than 30 wppm acetoacetamide-N-sulfonic acid), andthe finished acesulfame potassium composition comprises from 10 wppb to15 wppm acetoacetamide (and optionally less than 30 wppmacetoacetamide-N-sulfonic acid).

In another particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature below 46° C., the evaporatorresidence time is less than 30 minutes, the crystallizing is conductedat a temperature below 35° C., the intermediate acesulfame potassiumcomposition comprises from 10 wppb to 12 wppm acetoacetamide (andoptionally less than 20 wppm acetoacetamide-N-sulfonic acid), and thefinished acesulfame potassium composition comprises from 10 wppb to 7wppm acetoacetamide.

In another particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature ranging from 25° C. to 90°C., evaporator residence time ranges from 10 seconds to 180 minutes, theseparating operation, e.g., the crystallization and/or filtration, isconducted at a temperature ranging from −10° C. to 35° C., theseparating operation residence time ranges from 10 seconds to 180minutes, the crude acesulfame potassium composition comprises 1 wppm to2800 wppm acetoacetamide and 1 wppm to 2800 wppmacetoacetamide-N-sulfonic acid, the intermediate acesulfame potassiumcomposition comprises 1 wppb to 33 wppm acetoacetamide and 1 wppb to 33wppm acetoacetamide-N-sulfonic acid, and the finished acesulfamepotassium composition comprises 1 wppb to 33 wppm acetoacetamide, and 1wppb to 33 wppm acetoacetamide-N-sulfonic acid.

In another particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature ranging from 25° C. to 90°C., evaporator residence time ranges from 10 seconds to 180 minutes, theseparating operation, e.g., the crystallization and/or filtration, isconducted at a temperature ranging from −10° C. to 35° C., theseparating operation residence time ranges from 10 seconds to 180minutes, the crude acesulfame potassium composition comprises 1 wppm to2800 wppm acetoacetamide and 1 wppm to 2800 wppmacetoacetamide-N-sulfonic acid, the intermediate acesulfame potassiumcomposition comprises 1 wppb to 33 wppm acetoacetamide and 1 wppb to 33wppm acetoacetamide-N-sulfonic acid, and the finished acesulfamepotassium composition comprises 1 wppb to 33 wppm acetoacetamide, and 1wppb to 33 wppm acetoacetamide-N-sulfonic acid.

In another particular embodiment, the concentrating operation, e.g., theevaporation, is conducted at a temperature ranging from 20° C. to 55°C., evaporator residence time ranges from 1 minute to 300 minutes, theseparating operation, e.g., the crystallization and/or filtration, isconducted at a temperature ranging from −10° C. to 15° C., theseparating operation residence time ranges from 1 to 180 minutes, thecrude acesulfame potassium composition comprises from 500 wppm to 2375wppm acetoacetamide, the intermediate acesulfame potassium compositioncomprises 10 wppb to 20 wppm acetoacetamide and 10 wppb to 20 wppmacetoacetamide-N-sulfonic acid, and the finished acesulfame potassiumcomposition comprises from 10 wppb to 10 wppm acetoacetamide, and from 1wppb to 20 wppm acetoacetamide-N-sulfonic acid.

The acesulfame potassium compositions (crude and/or finished) may, insome cases, comprise organic impurities. Organic impurities include,inter alia, halo-acesulfame potassium. The acesulfame potassiumcompositions (crude and/or finished) also may comprise heavy metals. Theorganic impurities and/or heavy metals may be present in an amountranging from 1 wppb to 25 wppm, based on the total weight of therespective acesulfame potassium composition, crude or finished, e.g.,from 100 wppb to 20 wppm, from 100 wppb to 15 wppm, from 500 wppb to 10wppm, or from 1 wppm to 5 wppm. Heavy metals are defined as metals withrelatively high densities, e.g., greater than 3 g/cm³ or greater than 7g/cm³. Exemplary heavy metals include lead and mercury. In some cases,the crude or finished acesulfame potassium composition may comprisemercury in an amount ranging from 1 wppb to 25 wppm, e.g., from 100 wppbto 20 wppm, from 100 wppb to 15 wppm, from 500 wppb to 10 wppm, or from1 wppm to 5 wppm. In terms of limits, the crude or finished acesulfamepotassium composition may comprise less than 25 wppm mercury, e.g., lessthan 20 wppm, less than 15 wppm, less than 10 wppm, or less than 5 wppm.In some cases, the crude or finished acesulfame potassium compositionmay comprise lead in an amount ranging from 1 wppb to 25 wppm, e.g.,from 100 wppb to 20 wppm, from 100 wppb to 15 wppm, from 500 wppb to 10wppm, or from 1 wppm to 5 wppm. In terms of limits, the crude orfinished acesulfame potassium composition may comprise less than 25 wppmlead, e.g., less than 20 wppm, less than 15 wppm, less than 10 wppm, orless than 5 wppm. In some cases, when potassium hydroxide is formed viaa membrane process, the resultant crude or finished acesulfame potassiumcomposition may have very low levels of mercury, if any, e.g., less than10 wppm, less than 5 wppm, less than 3 wppm, less than 1 wppm, less than500 wppb, or less than 100 wppb.

Intermediate Reaction Parameters

The reactions for production of high purity acesulfame potassium aredescribed in more detail below.

Amidosulfamic Acid Salt Formation Reaction

In a first reaction step, sulfamic acid and an amine are reacted to formsulfamic acid salt. An exemplary reaction scheme that employstriethylamine as the amine and yields triethyl ammonium sulfamic acidsalt is shown in reaction (1), below.H₂N—SO₃H+N(C₂H₅)₃→H₂N—SO₃ ⁻.HN⁺(C₂H₅)₃  (1)

Acetic acid is also present in the first reaction mixture and reactswith the amine, e.g., triethylamine, to form a triethylammonium acetate,as shown in reaction (2), below.H₃C—COOH+N(C₂H₅)₃→H₃C—COO⁻.HN⁺(C₂H₅)₃  (2)

The amine employed in these reactions may vary widely. Preferably, theamine comprises triethylamine. In one embodiment, the amine may beselected from the group consisting of trimethylamine,diethylpropylamine, tri-n-propylamine, triisopropylamine,ethyldiisopropylamine, tri-n-butylamine, triisobutylamine,tricyclohexylamine, ethyldicyclohexylamine, N,N-dimethylaniline,N,N-diethylaniline, benzyldimethylamine, pyridine, substituted pyridinessuch as picoline, lutidine, cholidine or methylethylpyridine,N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine,N,N-dimethylpiperazine, 1,5-diazabicyclo[4.3.0]-non-5-en,1,8-diazabicyclo-[5.4.0]-undec-7-en, 1,4-diazabicyclooctane,tetramethylhexamethylendiamine, tetramethylethylendiamine,tetramethylpropylendiamine, tetramethylbutylendiamine,1,2-dimorpholylethan, pentamethyldiethyltriamine,pentaethyldiethylentriamine, pentamethyldipropylentriamine,tetramethyldiaminomethane, tetrapropyldiaminomethane,hexamethyltriethylentetramine, hexamethyltripropylenetetramine,diisobutylentriamine, triisopropylentriamine, and mixtures thereof.

Acetoacetamide Salt Formation Reaction

Once formed in reaction (1), the sulfamic acid salt is reacted with theacetoacetylating agent to form the acetoacetamide salt, preferablyacetoacetamide-N-sulfonate triethylammonium salt. Preferably, theacetoacetylating agent comprises diketene, although otheracetoacetylating agents may be employed, either with or withoutdiketene.

In one embodiment, the resultant acetoacetamide salt corresponds to thefollowing formula (3).

wherein M⁺ is an appropriate ion. Preferably, M⁺ is an alkali metal ionor N⁺R₁R₂R₃R₄. R₁, R₂, R₃ and R₄, independently of one another, may beorganic radicals or hydrogen, preferably H or C₁-C₈ alkyl, C₆-C₁₀cycloalkyl, aryl and/or aralkyl. In a preferred embodiment, R₁ ishydrogen, and R₂, R₃ and R₄ are alkyl, e.g., ethyl.

An exemplary reaction scheme for forming an acetoacetamide salt employsa trialkyl ammonium amidosulfamic acid salt and diketene as reactantsand yields an acetoacetamide triethylammonium salt is shown in reaction(4), below.

In one embodiment, the reaction is conducted in the presence of acatalyst, which may vary widely. In some embodiments, the catalystcomprises one or more amines and/or phosphines. Preferably, the catalystcomprises triethylamine. In some cases trimethylamine serves as both acatalyst and a reactant.

In one embodiment, wherein the amidosulfamic acid salt formationreaction and the acetoacetamide salt formation reaction are conducted inseparate reactors, a second reaction mixture comprises the amidosulfamicacid salt, the diketene, and the catalyst, e.g., triethylamine.Preferably, catalyst from the first reaction is carried through to thereaction mixture of the second reaction. The second reaction mixture isthen subjected to conditions effective to form the acetoacetamide salt.

In one embodiment, the composition of the second reaction mixture may besimilar to that of the first reaction mixture. In a preferredembodiment, the reaction product of the amidosulfamic acid saltformation reaction provides the amidosulfamic acid salt component of thesecond reaction mixture. In addition to the above-mentioned components,the second reaction mixture may further comprise reaction by-productsfrom the first reaction or non-reacted starting materials.

In one embodiment, the amount of acetoacetylating agent, e.g., diketene,should be at least equimolar to the reactant amidosulfamic acid saltthat is provided. In one embodiment, the process may utilize a diketenein excess, but preferably in an excess less than 30 mol %, e.g., lessthan 10 mol %. Greater excesses are also contemplated.

The amidosulfamic acid salt formation reaction and/or the acetoacetamidesalt formation reaction may employ an organic solvent. Suitable inertorganic solvents include any organic solvents that do not react in anundesired manner with the starting materials, cyclizing agent, finalproducts and/or the catalysts in the reaction. The solvents preferablyhave the ability to dissolve, at least partially, amidosulfamic acidsalts. Exemplary organic solvents include halogenated aliphatichydrocarbons, preferably having up to 4 carbon atoms such as, forexample, methylene chloride, chloroform, 1,2-dichlorethane,trichloroethylene, tetrachloroethylene, trichlorofluoroethylene;aliphatic ketones, preferably those having 3 to 6 carbon atoms such as,for example, acetone, methyl ethyl ketone; aliphatic ethers, preferablycyclic aliphatic ethers having 4 or 5 carbon atoms such as, for example,tetrahydrofuran, dioxane; lower aliphatic carboxylic acids, preferablythose having 2 to 6 carbon atoms such as, for example, acetic acid,propionic acid; aliphatic nitriles, preferably acetonitrile;N-alkyl-substituted amides of carbonic acid and lower aliphaticcarboxylic acids, preferably amides having up to 5 carbon atoms such as,for example, tetramethylurea, dimethylformamide, dimethylacetamide,N-methylpyrrolidone; aliphatic sulfoxides, preferably dimethylsulfoxide, and aliphatic sulfones, preferably sulfolane.

Particularly preferred solvents include dichloromethane (methylenechloride), 1,2-dichloroethane, acetone, glacial acetic acid anddimethylformamide, with dichloromethane (methylene chloride) beingparticularly preferred. The solvents may be used either alone or in amixture. In one embodiment, the solvent is a halogenated, aliphatichydrocarbon solvent, preferably the solvent is dichloromethane.Chloroform and tetrachloromethane are also exemplary solvents.

In one embodiment, the acetoacetamide salt formation reaction isconducted a temperature ranging from −30° C. to 50° C., e.g., from 0° C.to 25° C. The reaction pressure may vary widely. In preferredembodiments, the reaction is carried out at atmospheric pressure,although other pressures are also contemplated. The reaction time mayvary widely, preferably ranging from 0.5 hours to 12 hours, e.g., from 1hour to 10 hours. In one embodiment, the reaction is carried out byintroducing the amidosulfamic acid salt and metering in the diketene. Inanother embodiment, the reaction is carried out by introducing diketeneand metering in the amidosulfamic acid salt. The reaction may be carriedout by introducing the diketene and amidosulfamic acid and metering inthe catalyst.

Once formed, each reaction product is optionally subjected to one ormore purification steps. For example the solvent may be separated fromthe reaction product, e.g., via distillation, and the residue (mainlyacetoacetamide-N-sulfonate) may be recrystallized from a suitablesolvent such as, for example, acetone, methyl acetate or ethanol.

Cyclization and Hydrolyzation

The acetoacetamide salt is reacted with cyclizing agent, e.g., cyclizingagent in the cyclizing agent composition, in the presence of a solventto form the cyclic (sulfur trioxide) adduct composition, which containscyclic sulfur trioxide adduct and, in some cases, impurities. In somecases, a cooling step occurs before the cyclic sulfur trioxide adductformation reaction. In one embodiment, the cyclization is achieved byusing at least an equimolar amount of the cyclizing agent. The cyclizingagent may be dissolved in an inert inorganic or organic solvent. Thecyclizing agent is generally used in a molar excess, e.g., up to a 20fold excess, or up to a 10 fold excess, based on the total moles ofacetoacetamide salt. An exemplary cyclization reaction using sulfurtrioxide as the cyclizing agent is shown in reaction (5), below.

In one embodiment, the weight ratio of solvent to cyclizing agent in thecyclizing agent composition is at least 1:1, e.g., at least 2:1, or atleast 5:1. In one embodiment, the weight ratio of solvent to cyclizingagent in the cyclizing agent composition ranges from 1:1 to 25:1, e.g.,from 1:1 to 10:1, from 2:1 to 10:1, or from 5:1 to 10:1.

A cyclizing agent may be any compound that initiates the ring closure ofthe acetoacetamide salt. Although sulfur trioxide is a preferredcyclizing agent, the employment of other cyclizing agents iscontemplated.

The cyclizing agent may be added to the reaction mixture either in thesolid or the liquid form or by condensing in vapor. Suitable inertinorganic or organic solvents are those liquids which do not react in anundesired manner with sulfur trioxide or the starting materials or finalproducts of the reaction. Preferred organic solvents include, but arenot limited to, halogenated aliphatic hydrocarbons, preferably having upto four carbon atoms, such as, for example, methylene chloride(dichloromethane), chloroform, 1,2-dichloroethane, trichloroethylene,tetrachloroethylene, trichlorofluoroethylene; esters of carbonic acidwith lower aliphatic alcohols, preferably with methanol or ethanol;nitroalkanes, preferably having up to four carbon atoms, in particularnitromethane; alkyl-substituted pyridines, preferably collidine; andaliphatic sulfones, preferably sulfolane. Particularly preferredsolvents for the cyclization reaction include dichloromethane (methylenechloride), 1,2-dichloroethane, acetone, glacial acetic acid anddimethylformamide, with dichloromethane (methylene dichloride) beingparticularly preferred. Other solvents, e.g., other solvents mentionedherein, may also be suitable as solvents. The solvents may be usedeither alone or in a mixture. In one embodiment, the solvent is ahalogenated, aliphatic hydrocarbon solvent, preferably the solvent isdichloromethane. The processes may employ these solvents alone or inmixtures thereof.

In some cases, the solvent in the cyclizing agent composition may beselected from 1) concentrated sulfuric acid, 2) liquid sulfur dioxide,or 3) an inert organic solvent.

In a preferred embodiment, the same solvent is used in both theacetoacetamide salt formation reaction and the cyclization reaction. Asone benefit, the solution obtained in the acetoacetamide salt formationreaction, without isolation of the acetoacetamide salt formationreaction product, may be used immediately in the cyclization.

In one embodiment, the reaction temperature for the cyclization reactionranges from −70° C. to 175° C., e.g., from −40° C. to 60° C. Thepressure at which the reaction is conducted may vary widely. In oneembodiment, the reaction is conducted at a pressure ranging from 0.01MPa to 10 MPa, e.g., from 0.1 MPa to 5 MPa. Preferably, the reaction isconducted at atmospheric pressure.

The acetoacetamide salt may be introduced to the cyclization reactor andthe cooled cyclizing agent composition, e.g., a solution of cyclizingagent optionally in solvent, may be metered into the reactor. Inpreferred embodiments, both reactants (acetoacetamide salt and cyclizingagent) are simultaneously fed into the reactor. In one embodiment, thecooled cyclizing agent composition is initially introduced into thereactor and the acetoacetamide salt is added. Preferably, at least partof the cyclizing agent composition is introduced into the reactor and,either continuously or in portions, acetoacetamide salt and (additional)cyclizing agent are then metered in, preferably while maintaining thetemperature as described above.

The acetoacetamide salt may be introduced to the reactor and thecyclizing agent composition may be metered into the reactor. Inpreferred embodiments, both reactants are simultaneously fed into thereactor. In one embodiment, the cyclizing agent composition is initiallyintroduced into the reactor and the acetoacetamide salt is added.Preferably, at least part of the cyclizing agent composition isintroduced into the reactor and, either continuously or in portions,acetoacetamide salt and (additional) cyclizing agent are then meteredin, preferably while maintaining the temperature as described above.

The formation of the crude acesulfame potassium composition from thecyclic sulfur trioxide adduct composition, in some embodiments,comprises the steps of hydrolyzing the cyclic sulfur trioxide adduct toform an acesulfame-H composition; neutralizing the acesulfame-H in theacesulfame H composition to form a crude acesulfame potassiumcomposition; and forming the acesulfame potassium composition from thecrude acesulfame potassium composition.

The cyclic sulfur trioxide adduct may be hydrolyzed via conventionalmeans, e.g., using water. Thus, the forming step may comprise the stepsof hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-Hcomposition. Acesulfame-H is referred to as sweetener acid.

An exemplary hydrolysis reaction scheme is shown in reaction (6), below.

The addition of the water leads to a phase separation. The majority ofthe sweetener acid, acesulfame-H(6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide), which isformed via the hydrolysis, is present in the organic phase, e.g., atleast 60 wt %, at least 70%, at least 80%, or at least 90%. Theremainder of the sweetener acid is in the water phase and can beextracted and optionally added to the sweetener acid in the organicphase. In cases where dichloromethane is used as the reaction medium,water or ice may be added, e.g., in a molar excess, based on the sulfurtrioxide, to the cyclic sulfur trioxide adduct/sulfur trioxide solution.

In some cases, the hydrolysis step comprises adding water to the cyclicsulfur trioxide adduct. In preferred embodiments, the weight ratio ofwater to acetoacetamide salt is greater than 1.3:1, e.g., greater than1.5:1, greater than 1.7:1, greater than 2:1 or greater than 2.2:1.Employment of these ratios may lead to decreases inacetoacetamide-N-sulfonic acid and/or acetoacetamide formation in theneutralized crude acesulfame potassium composition, e.g., the crudeacesulfame potassium composition may comprise acetoacetamide-N-sulfonicacid in the amounts discussed herein.

It was surprisingly discovered that the temperature at which the wateris initially fed to the hydrolysis reaction may have beneficial effectson impurity production, e.g., organic production or 5-chloro-acesulfamepotassium production as well as reaction parameters, e.g., temperature.At lower temperatures, e.g., lower than approximately −35° C. or lowerthan −22° C., ice tends to build up in the reaction mixture. As this icemelted, it led to the onset of additional reaction, which caused thetemperature to rise quickly. This rise in temperature surprisingly ledto a product that contained much higher levels of impurities. In somecases, the hydrolyzing comprises adding hydrolysis water to the cyclicsulfur trioxide adduct to form a hydrolysis reaction mixture andreacting the mixture to from the acesulfame-H composition. In someembodiments, the temperature of the hydrolysis reaction mixture or thetemperature at which the hydrolysis water is fed to the reactor ismaintained at a temperature greater than −35° C., e.g., greater than−30° C., greater than −25° C., greater than −24° C., greater than −23°C., greater than −22° C., greater than −21.5° C., greater than −21° C.,or greater than greater than −20° C. In terms of ranges, the temperatureof the hydrolysis reaction mixture or the temperature at which thehydrolysis water is fed to the reactor optionally is maintained at atemperature ranging from −35° C. to 0° C., e.g., from −30° C. to −5° C.,from −20° C. to −5° C., from −30° C. to −20° C., from −25° C. to −21°C., or −25° C. to −21.5° C.

After the addition of water, the reaction solvent, e.g.,dichloromethane, may be removed by distillation, or the acesulfame-Hthat remains in the organic phase may be extracted with a more suitablesolvent. Suitable solvents are those which are sufficiently stabletowards sulfuric acid and which have a satisfactory dissolving capacity.Other suitable solvents include esters of carbonic acid such as, forexample dimethyl carbonate, diethyl carbonate and ethylene carbonate, oresters of organic monocarboxylic acids such as, for example, isopropylformate and isobutyl formate, ethyl acetate, isopropyl acetate, butylacetate, isobutyl acetate and neopentyl acetate, or esters ofdicarboxylic acids or amides which are immiscible with water, such as,for example, tetrabutylurea, are suitable. Isopropyl acetate andisobutyl acetate are particularly preferred.

It has now been discovered that a transition phase may form in additionto the organic sweetener acid-dichloromethane phase and aqueous phase.The transition phase may contain high amounts of impurities, e.g.,acetoacetamide. The transition phase may contain higher amounts of suchimpurities than the organic phase. Beneficially, this transition phasemay be removed from the organic sweetener acid-dichloromethane phasethus significantly reducing impurity content thereof. The process mayutilize the step of phase separating the acesulfame-H composition. Thephase separation may form the sweetener acid-dichloromethane phase, theaqueous phase, and the aforementioned transition phase comprising atleast 2 wt % impurities, e.g., at least 5 wt %, at least 10 wt %, atleast 20 wt %, at least 30 wt %, or at least 50 wt %. The process maycomprise separating from the acesulfame-H composition the transitionphase to form a purified acesulfame-H composition. The finishedacesulfame potassium composition may then be formed from the purifiedacesulfame-H composition, e.g., via neutralization and treatment.

The combined organic phases are dried with, for example, Na₂SO₄, and areevaporated. Any sulfuric acid which has been carried over in theextraction may be removed by appropriate addition of aqueous alkali tothe organic phase. For this purpose, dilute aqueous alkali may be addedto the organic phase until the pH reached in the aqueous phasecorresponds to that of pure 6-methyl-3,4-dihydro1,2,3-oxathiazin-4-one2,2-dioxide at the same concentration in the same two-phase system ofextracting agent and water.

Neutralization

The neutralization of the acesulfame-H yields a non-toxic salt ofacesulfame-H, e.g., acesulfame potassium. In one embodiment,neutralization is carried out by reacting the acesulfame-H with anappropriate base, e.g., potassium hydroxide, in particular amembrane-produced potassium hydroxide. Other suitable bases include, forexample, KOH, KHCO₃, K₂CO₃, and potassium alcoholates. An exemplaryreaction scheme using potassium hydroxide as a neutralizing agent isshown in reaction (7), below.

In some cases, the neutralization is conducted or maintained at a low pHlevels, which may advantageously further result in a reduction orelimination of the formation of impurities, e.g., acetoacetamide salts.In this context, “conducted” means that the neutralization step beginsat a low pH level, and “maintained” means that steps are taken to ensurethat the pH stays within a low pH range throughout the entireneutralization step. In one embodiment, the neutralization step isconducted or maintained at a pH below 10.0, e.g., below 9.5, below 9.0,below 8.5, below 8.0, below 7.5, below 7.0, or below 6.5. In terms ofranges, the neutralization step is preferably conducted or maintained ata pH between 6.0 and 10.0, e.g., between 6.5 and 9.5, between 7.0 and9.0, or between 7.5 and 8.5.

In some cases, the pH in the neutralizing step may be maintained withinthe desired range by managing the components of the neutralizationreaction mixture, which comprises acesulfame-H and neutralizing agent(and also solvent). For example, the composition of the neutralizationreaction mixture may include from 1 wt % to 95 wt % neutralizing agent,e.g., from 10 wt % to 85 wt % or from 25 wt % to 75 wt %, and from 1 wt% to 95 wt % acesulfame-H, e.g., from 10 wt % to 85 wt % or from 25 wt %to 75 wt %. These concentration ranges are based on the mixture ofneutralization agent and acesulfame-H (not including solvent).

In one embodiment, the acesulfame-H may be neutralized and extracteddirectly from the purified organic extraction phase using an aqueouspotassium base. The acesulfame potassium then precipitates out, whereappropriate after evaporation of the solution, in the crystalline form,and it can also be recrystallized for purification.

In one embodiment, the process is not a small-scale batch process or alaboratory-scale process. For example, the inventive process forproducing a finished acesulfame potassium composition may yield at least50 grams of finished acesulfame potassium composition per batch, e.g.,at least 100 grams per batch, at least 500 grams per batch, at least 1kilogram per batch, or at least 10 kilograms per batch. In terms ofrates, the inventive process may yield at least 50 grams of finishedacesulfame potassium composition per hour, e.g., at least 100 grams perhour, at least 500 grams per hour, at least 1 kilogram per hour, or atleast 10 kilograms per hour.

FIG. 1 shows an exemplary acesulfame potassium process 100 in accordancewith the process described herein. Process 100 comprises amidosulfamicacid salt formation reactor 102 and acetoacetamide salt formationreactor 104. Although FIG. 1 shows separate reactors for the twointermediate formation reactions, other configurations, e.g., a onereactor process, are within the contemplation of the present process.Sulfamic acid is fed to amidosulfamic acid salt formation reactor 102via sulfamic acid feed line 106. Amine(s), preferably triethylamine, arefed to amidosulfamic acid salt formation reactor 102 via amine feed line108. In addition to sulfamic acid and amine(s), acetic acid is also fedto amidosulfamic acid salt formation reactor 102 (via feed line 110).The resultant reaction mixture in amidosulfamic acid salt formationreactor 102 is as discussed above. In amidosulfamic acid salt formationreactor 102, the sulfamic acid and the amine (in the presence of theacetic acid) are reacted to yield a crude amidosulfamic acid saltcomposition, which exits reactor 102 via line 112. Although not shown, areaction solvent, e.g., dichloromethane may also be present in theamidosulfamic acid salt formation reactor 102.

The crude amidosulfamic acid salt composition in line 112 is directed toacetoacetamide salt formation reactor 104. Diketene is fed toacetoacetamide salt formation reactor 104 via feed line 114. Inacetoacetamide salt formation reactor 104, the amidosulfamic acid saltand the diketene are reacted to yield a crude acetoacetamide saltcomposition, which exits reactor 104 via line 118. Although not shown,dichloromethane may also be present in the acetoacetamide salt formationreactor 104.

Cyclizing agent (sulfur dioxide) and solvent (dichloromethane) are fedto vessel 119 via feed lines 121 and 123. Vessel 119 is preferably avessel wherein a cyclizing agent composition comprising these twocomponents is formed. The cyclizing agent composition comprising bothcyclizing agent and solvent exits vessel 119 via line 125.

The crude acetoacetamide salt composition is directed to cyclizationreactor 120 via line 118. The cyclizing agent composition is alsodirected to cyclization reactor 120 (via line 125). Line 125 ispreferably made of a material and in such a size and shape to facilitatethe residence times discussed herein. In cyclization reactor 120, theacetoacetamide salt in the crude acetoacetamide salt composition in line118 is cyclized and a cyclic sulfur trioxide adduct stream exits vialine 124.

The cyclic sulfur trioxide adduct in line 124, is directed to hydrolysisreactor 126. Water is fed to hydrolysis reactor 126 via water feed 128.In hydrolysis reactor 126, the cyclic sulfur trioxide adduct ishydrolyzed to yield a crude acesulfame-H composition, which exitshydrolysis reactor 126 via line 130 and is directed to phase separationunit 132. Phase separation unit 132 separates the contents of line 130into organic phase 134 and aqueous phase 136. Organic phase 134comprises a major amount of the acesulfame-H in line 130 as well assolvent, e.g., methylene chloride. Aqueous phase 136 exits via line 137and comprises triethylammonium sulfate, and optionally sulfuric acid andminor amounts of acesulfame-H. The aqueous phase may be further purifiedto separate and/or recover the acesulfame-H and/or the triethylammoniumsulfate. The recovered acesulfame-H may be combined with the acesulfamefrom the organic phase (not shown).

Organic phase 134 exits phase separation unit 132 and is directed toextraction column 138 (via line 140). Water is fed to extraction column138 via water feed 142. The water extracts residual sulfates from thecontents of line 140 and a purified acesulfame-H composition exitsextraction column 138 via line 144. The extracted sulfates exitextraction column 138 via line 145.

The purified acesulfame-H composition in line 144 is directed toneutralization unit 146. Potassium hydroxide is also fed toneutralization unit 146 (via line 148). The addition of the potassiumhydroxide (via line 148) to neutralization unit 146 may be adjusted toachieve and/or maintain the desired pH levels during the neutralization,as discussed herein. The potassium hydroxide neutralizes theacesulfame-H in the purified acesulfame-H composition to yield a productcomprising acesulfame potassium, dichloromethane, water, potassiumhydroxide, and impurities, e.g., acetoacetamide, which exitsneutralization unit 146 via line 150. This product may be considered acrude acesulfame potassium composition.

The crude acesulfame potassium product stream in line 150 may bedirected to treatment zone 156 to recover finished acesulfame potassium,which is shown exiting via stream 152. In addition to the finishedacesulfame potassium, dichloromethane and potassium hydroxide may beseparated from the crude acesulfame potassium product stream, as shownby stream 154. The contents of stream 154 may be recovered and/orrecycled to the process. Treatment zone 156 may comprise one or more ofthe treatment steps described herein, e.g., stripping, evaporation,crystallization, and filtration.

The product in line 150 is directed to phase separation unit 160. Phaseseparation unit 160 separates the product in line 150 into organic phase162 and an aqueous phase 164. Aqueous phase 164 comprises a major amountof the acesulfame potassium in line 150 as well as some impurities.Organic phase 162 comprises potassium hydroxide, dichloromethane, andwater and may be further treated to recover these components. Aqueousphase 164 (without any further treatment) may be considered a crudeacesulfame potassium composition. Aqueous phase 164 may be optionallytreated to form a finished acesulfame potassium composition.

Aqueous phase 164 is directed to treatment unit 156 via line 166. Intreatment unit 156, aqueous phase 164 is treated to obtain finishedacesulfame potassium composition (product that may be sold), which isshown exiting via stream 152. In addition to the finished acesulfamepotassium composition, dichloromethane and potassium hydroxide may beseparated. These components exit treatment unit 156 via line 154. Thecontents of stream 154 may be recovered and/or recycled to the process.

FIG. 2 shows and exemplary treatment zone. Crude acesulfame potassiumproduct stream 250 is fed to treatment zone 256. In particular, crudeacesulfame potassium product stream 250 is fed to stripper 252 to stripsolvent therefrom. Solvent in stream 254 exits stripper 252 and isdirected to further processing, e.g. re-use or recycling. Strippedacesulfame potassium stream 257 comprises low amounts of solvent andexits stripper 252 and is directed to evaporator 258. It has been foundthat the removal of solvent prior to evaporation unexpectedly providesthe benefit of improved evaporation operations.

Evaporator 258 removes water from stripped acesulfame potassium streamin line 257 to form water stream 260 and intermediate acesulfamepotassium composition stream 262. Evaporator 258 is preferably a fallingfilm evaporator. Intermediate acesulfame potassium composition stream262 is directed to crystallizer 264, which yields crystal-containingstream 266 and recycle stream 268. Crystal-containing stream 266 is thendirected to filtration unit 270, which filters impurities to yieldfinished acesulfame potassium composition stream 272 and impurity stream274. The treatment units may beneficially be operated at the separationparameters discussed herein.

The invention relates also to the following aspects:

Aspect 1: A process for producing a finished acesulfame potassiumcomposition, the process comprising the steps of:

-   -   (a) providing a crude acesulfame potassium composition        comprising acesulfame potassium, acetoacetamide and water;    -   (b) concentrating the crude acesulfame potassium composition to        form a water stream and an intermediate acesulfame potassium        composition comprising acesulfame potassium and less than 33        wppm acetoacetamide; and    -   (c) separating the intermediate acesulfame potassium composition        to form the finished acesulfame potassium composition comprising        acesulfame potassium and less than 33 wppm acetoacetamide;

wherein the concentrating step (b) is conducted at a temperature below90° C., and wherein the separating step (c) is conducted at atemperature at or below 35° C.

Aspect 2: The process of aspect 1, wherein the providing step (a)comprises:

reacting sulfamic acid and an amine to form an amidosulfamic acid salt;

reacting the amidosulfamic acid salt and acetoacetylating agent to forman acetoacetamide salt;

reacting the acetoacetamide salt with cyclizing agent in the cyclizingagent composition to form the cyclic sulfur trioxide adduct;

hydrolyzing the cyclic sulfur trioxide adduct to form an acesulfame-Hcomposition comprising acesulfame-H; and

neutralizing the acesulfame-H in the acesulfame-H composition to formthe crude acesulfame potassium composition.

Aspect 3: The process of any one of the preceding aspects, wherein theintermediate acesulfame potassium composition comprises less than 33wppm acetoacetamide-N-sulfonic acid.

Aspect 4: The process of any one of the preceding aspects, wherein theconcentrating comprises: evaporating the crude acesulfame potassiumcomposition to form the water stream and the intermediate acesulfamepotassium composition comprising acesulfame potassium and less than 75wt % water.

Aspect 5: The process of any one of the preceding aspects, whereinevaporation residence time is less than 180 minutes.

Aspect 6: The process of any one of the preceding aspects, wherein theintermediate acesulfame potassium composition comprises less than 33wppm acetoacetamide-N-sulfonic acid.

Aspect 7: The process of any one of the preceding aspects, wherein theseparating comprises:

crystallizing the intermediate acesulfame potassium composition to formacesulfame potassium crystals; and

filtering the acesulfame potassium crystals to form the finishedacesulfame potassium composition.

Aspect 8: The process of any one of the preceding aspects, wherein thefiltering is conducted at a temperature at or below 35° C.

Aspect 9: The process of any one of the preceding aspects, wherein thecrystallizing is conducted at a temperature at or below 35° C.

Aspect 10: The process of any one of the preceding aspects, wherein thecrystallizing is conducted at a pH below 10.

Aspect 11: The process of any one of the preceding aspects, wherein theevaporating is conducted at a temperature below 85° C. and theintermediate acesulfame potassium composition comprises from 1 wppb to33 wppm acetoacetamide and the finished acesulfame potassium compositioncomprises less than 33 wppm acetoacetamide.

Aspect 12: The process of any one of the preceding aspects, wherein theintermediate acesulfame potassium composition further comprises lessthan 33 wppm acetoacetamide-N-sulfonic acid.

Aspect 13: The process of any one of the preceding aspects, wherein theevaporating is conducted at a temperature below 60° C. and theevaporator residence time is less than 50 minutes and the intermediateacesulfame potassium composition comprises from 10 wppb to 25 wppmacetoacetamide and the finished acesulfame potassium compositioncomprises from 10 wppb to 15 wppm acetoacetamide.

Aspect 14: The process of any one of the preceding aspects, wherein theintermediate acesulfame potassium composition comprises less than 30wppm acetoacetamide-N-sulfonic acid.

Aspect 15: The process of any one of the preceding aspects, wherein theevaporating is conducted at a temperature ranging from 20° C. to 55° C.;the evaporator residence time ranges from 1 minute to 300 minutes; theseparating is conducted at a temperature ranging from −10° C. to 15° C.;the separating operation residence time ranges from 1 to 180 minutes;the crude acesulfame potassium composition comprises from 500 wppm to2375 wppm acetoacetamide; the intermediate acesulfame potassiumcomposition comprises 10 wppb to 20 wppm acetoacetamide and 10 wppb to20 wppm acetoacetamide-N-sulfonic acid; and the finished acesulfamepotassium composition comprises from 10 wppb to 10 wppm acetoacetamide,and from 1 wppb to 20 wppm acetoacetamide-N-sulfonic acid.

Aspect 16: The process of any one of the preceding aspects, wherein:

(i) the evaporating is conducted at a temperature below 46° C.,

(ii) the evaporator residence time is less than 30 minutes,

(iii) crystallizing is conducted at a temperature below 35° C.,

(iv) the intermediate acesulfame potassium composition comprises from 10wppb to 12 wppm acetoacetamide, and

(v) the finished acesulfame potassium composition comprises from 10 wppbto 7 wppm acetoacetamide.

Aspect 17: The process of any one of the preceding aspects, wherein theintermediate acesulfame potassium composition comprises less than 20wppm acetoacetamide-N-sulfonic acid.

Aspect 18: The process of any one of the preceding aspects, wherein thecrude acesulfame composition further comprises solvent and wherein theprocess further comprises removing solvent from the crude acesulfamepotassium composition prior to the evaporation.

Aspect 19: The process of any one of the preceding aspects, wherein theweight percentage of acetoacetamide in the finished acesulfame potassiumcomposition is less than the weight percentage of acetoacetamide in thecrude acesulfame potassium composition.

Aspect 20: The process of any one of the preceding aspects, furthercomprising:

separating from the acesulfame-H composition a transition phasecomprising at least 2 wt % acetoacetamide to form a purifiedacesulfame-H composition.

Aspect 21: The process of any one of the preceding aspects, wherein theneutralizing comprises neutralizing the acesulfame-H in the purifiedacesulfame-H composition to form the crude acesulfame potassiumcomposition comprising acesulfame potassium and acetoacetamide.

Aspect 22: The process of any one of the preceding aspects, wherein theconcentrating comprises evaporating the crude acesulfame potassiumcomposition to form a water stream and an intermediate acesulfamepotassium composition comprising acesulfame potassium and less than 50wt % water, and the separating comprises crystallizing the intermediateacesulfame potassium composition to form a crystal-containing streamcomprising acesulfame potassium crystals, and filtering thecrystal-containing stream to form the finished acesulfame potassiumcomposition.

Aspect 23: The process of any one of the preceding aspects, wherein thefiltering comprises at least two filtration operations.

Aspect 24: A finished acesulfame potassium composition produced orproducible by, or obtainable or obtained from the process of any one ofaspects 1 to 22.

Aspect 25: A process for producing a finished acesulfame potassiumcomposition, the process comprising the steps of:

-   -   (a) reacting sulfamic acid and triethylamine to form an        amidosulfamic acid salt;    -   (b) reacting the amidosulfamic acid salt and diketene to form        acetoacetamide salt;    -   (c) contacting dichloromethane and a sulfur trioxide to form a        cyclizing agent composition;    -   (d) reacting the acetoacetamide salt with sulfur trioxide in the        cyclizing agent composition to form a cyclic sulfur trioxide        adduct;    -   (e) hydrolyzing the cyclic sulfur trioxide adduct to form an        acesulfame-H composition;    -   (f) neutralizing the acesulfame-H to form the crude acesulfame        potassium composition comprising acesulfame potassium and        acetoacetamide,    -   (g) evaporating the crude acesulfame potassium composition to        form a water stream and an intermediate acesulfame potassium        composition comprising acesulfame potassium and less than 75 wt        % water;    -   (h) crystallizing the intermediate acesulfame potassium        composition to form acesulfame potassium crystals; and    -   (i) filtering the acesulfame potassium crystals to form the        finished acesulfame potassium composition comprising acesulfame        potassium and less than 10 wppm acetoacetamide, wherein the        evaporating is conducted at a temperature below 50° C. and        wherein evaporator residence time is less than 30 minutes.

Aspect 26: The process of aspect 25, wherein filtering is conducted at atemperature below 35° C. and crystallizing is conducted at a temperaturebelow 35° C.

Aspect 27: A finished acesulfame potassium composition produced orproducible by, or obtainable or obtained from the process of aspects 25or 25.

Aspect 28: An acesulfame potassium composition comprising acesulfamepotassium and less than 33 wppm, preferably less than 10 wppmacetoacetamide.

Aspect 29: The acesulfame potassium composition of aspect 27 or 28,further comprising less than 33 wppm, preferably less than 10 wppmacetoacetamide-N-sulfonic acid.

Aspect 30: The acesulfame potassium composition of aspect 27-29, furthercomprising 0.001 wppm to 5 wppm organic impurities and/or 0.001 wppm to5 wppm of at least one heavy metal.

Aspect 31: The acesulfame potassium composition of aspect 27-30, whereinthe at least one heavy metal is selected from the group consisting ofmercury, lead and mixtures thereof.

Aspect 31: The acesulfame potassium composition of aspect 27-31, whereinthe mercury is present in an amount of 1 wppb to 20 wppm.

Aspect 31: The acesulfame potassium composition of aspect 27-32, whereinthe lead is present in an amount of 1 wppb to 25 wppm.

EXAMPLES

The following examples are included to illustrate the process andcompositions and are not meant to limit the scope of the application.

Crude Acesulfame Potassium Composition Formation

100 mmol of 99.5% pure sulfamic acid was suspended in 50 mLdichloromethane in a flask with reflux. Under continuous agitation, 105mmol of trimethylamine was added within approximately 3 minutes. Duringthis time, temperature increased due to acid/base exothermal reaction upto about 42° C. (the boiling point of dichloromethane). This firstreaction mixture was stirred for approximately 15 additional minutes,until no solid sedimentation was seen in the flask. Then, 10 mmol ofacetic acid was added to the first reaction mixture and was stirred forapproximately 15 additional minutes. At this point, within 7 minutes ofthe addition of the acetic acid, 110 mmol of diketene was added dropwiseto form a second reaction mixture. After the addition of all of thediketene was added to the second reaction mixture and approximately 15minutes of reaction time, this second reaction mixture was cooled. Theresultant cooled second reaction mixture contained approximately 30%acetoacetamide N-sulfonate triethylammonium salt. Additional batches ofcooled second reaction mixture were prepared as necessary.

In a separate vessel, a sulfur trioxide/dichloromethane compositioncomprising approximately 15 wt % sulfur trioxide and approximately 85 wt% dichloromethane was prepared by contacting the two components with oneanother.

A second flask (a 4 necked round bottom flask equipped with mechanicalstirrer, thermometer, and feed vessels) was placed into a cooling bathcontaining a mixture of isopropanol and dry ice. Approximately 200 g ofthe acetoacetamide-N-sulfonate triethylammonium salt solution andapproximately 577 g of the sulfur trioxide/dichloromethane compositionswere measured. Approximately 15 wt % of the total sulfurtrioxide/dichloromethane composition (approximately 87 g) was initiallyfed to the reaction flask under continuous agitation by mechanicalstirrer. When the temperature of the flask contents reached −35° C. (dueto the cooling bath), the remainder of the sulfurtrioxide/dichloromethane composition and all of theacetoacetamide-N-sulfonate triethylammonium salt solution were fed intothe second flask. The time period that the solvent contacts thecyclizing agent before formation of the cyclic sulfur trioxide adduct,e.g., before the acetoacetamide-N-sulfonate triethylammonium saltsolution was fed to the second flask, was less than an hour. The feedrate was controlled in such a way that the temperature of the secondflask contents remained between −25° and −35° C. during thefeeding/cyclization reaction. After the reactants were fed, the reactionwas allowed to proceed for approximately one additional minute. Thecooling bath was then removed.

After approximately one minute, the temperature of the flask contentsreached approximately −22° C. At this time, hydrolysis was initiated byfeeding deionized water to the flask. Water was fed over 10 minutes. Thehydrolysis reaction was exothermic. Water was added slowly so as tomaintain temperature between −20° C. and −5° C. After addition of water,reaction mixture was allowed to reach room temperature.

The hydrolyzed product was phase separated via a separating funnel. Aheavier organic sweetener acid-dichloromethane phase (acesulfame-Hcomposition) was separated out, and the remaining aqueous phase wasdiscarded.

The acesulfame-H in the acesulfame-H composition was neutralized with a10% potassium hydroxide solution. Neutralization was carried out at 25°C.±1° C. Potassium hydroxide addition was completed within 20 minutes.After completion of the neutralization step, an additional phaseseparation was performed using a separating funnel to yield an aqueousphase containing acesulfame potassium (and some impurities) and anorganic phase. The aqueous phase was considered a crude acesulfamepotassium composition. This crude acesulfame potassium composition wassplit into two portions and treated as discussed below. The remainingdichloromethane in the organic phase was discarded.

Example 1: Evaporation/Crystallization

A first portion of the crude acesulfame potassium composition wasevaporated in a rotary evaporator at 45° C. and under reduced pressurefor approximately 20 minutes. As a result, approximately 50% of thewater was evaporated from the crude acesulfame potassium composition.After the water was removed an intermediate acesulfame potassiumcomposition remained. The intermediate acesulfame potassium compositionwas then separated, e.g., cooled to 5° C. in a refrigerator.

The cooling resulted in the precipitation of crude crystals containingmostly acesulfame potassium. These crude crystals were considered afinished acesulfame potassium composition. The crude crystals wereseparated from the liquid and analyzed for yield and impurities, e.g.,acetoacetamide. Testing for acetoacetamide (AAA) content was performedusing the HPLC equipment and techniques discussed herein. In particular,the HPLC analysis was performed using an LC Systems HPLC unit fromShimadzu having a CBM-20 Shimadzu controller and being equipped with anIonPac NS1 ((5 μm) 150×4 mm) analytical column and an IonPac NG1 guardcolumn (35×4.0 mm). A Shimadzu SPD-M20A photodiode array detector wasused for detection (at 270 nm and 280 nm wavelength). Analysis wasperformed at 23° C. column temperature. As a first eluent solution, anaqueous mixture of tetra butyl ammonium hydrogen sulfate (3.4 g/L),acetonitrile (300 mL/L), and potassium hydroxide (0.89 g/L) wasemployed; as a second eluent solution, an aqueous mixture of tetra butylammonium hydrogen sulfate (3.4 g/L) and potassium hydroxide (0.89 g/L)was employed. Elution was conducted in gradient mode according to thefollowing second eluent flow profile:

0 to 3 minutes: constant 80% (v/v)

3 to 6 minutes: linear reduction to 50% (v/v)

6 to 15 minutes: constant at 50% (v/v)

15 to 18 minutes: linear reduction to 0%

18 to 22 minutes: constant at 0%

22 to 24 minutes: linear increase to 80% (v/v)

24 to 35 minutes constant at 80% (v/v).

Overall flow rate of eluent was approximately 1.2 mL/min. The datacollection and calculations were performed using Lab Solution softwarefrom Shimadzu.

Comparative Example A: Evaporation/Crystallization

A second portion of the crude acesulfame potassium composition wasevaporated in a rotary evaporator at 90° C. and under reduced pressurefor approximately 180 minutes. As a result, approximately 50% of thewater was evaporated from the crude acesulfame potassium composition.After the water was removed an intermediate acesulfame potassiumcomposition remained. The intermediate acesulfame potassium compositionwas then separated, e.g., cooled to 5° C. in a refrigerator.

The cooling resulted in the precipitation of crude crystals containingmostly acesulfame potassium. These crude crystals were considered afinished acesulfame potassium composition. The crude crystals wereseparated from the liquid and analyzed for yield and impurities, e.g.,acetoacetamide. Testing for acetoacetamide content was performed usingthe HPLC equipment and techniques discussed above. The results forExample 1 and Comparative Example A are shown in Table 1.

TABLE 1 ACK Impurity Testing Immediately After FirstEvaporation/Crystallization AAA, wppm, in the Evap. Evap.Crystallization finished ACK Example 1 Temp., ° C. Time, min. Temp., °C. composition Comp. 45° C.  20 min. 5° C.  5 wppm Ex. A 90° C. 180 min.5° C. 37 wppm

The temperature of the concentrating of the crude acesulfame potassiumcomposition and the separating operation of the intermediate acesulfamepotassium composition have an influence on acetoacetamide formation.Without being bound by theory, it is believed that acetoacetamideimpurities form as a result of thermal stress during high temperatureconcentration of the crude acesulfame potassium composition, e.g.,during the initial evaporation step. As shown, if the temperature of theconcentrating operation is kept below 90° C., then additionalpost-crystallization separation is not needed to keep acetoacetamidecontent below a suitable level, e.g., less than 10 wppm.

Examples 2 and Comparative Examples B-D

The degradation effects of temperature and pH on acesulfame potassiumcompositions during treatment were also explored. Acesulfame potassiumwas diluted in sufficient water to form a 16% aqueous solution. Theaqueous solution was divided into multiple portions (Example 2 andComparative Examples B-D). These portions of aqueous solution (exceptfor Example 2) were heated under reflux condensing to simulate theconcentrating operation. In Comparative Example D, prior to heating, asmall amount of 10% potassium hydroxide was added to the respectiveportion of aqueous solution, which brought the pH of the resultantsolution to approximately 9.8. For each portion, crystals (intermediateacesulfame potassium compositions) were removed from the remainingliquid (after heating) and analyzed for and impurities formed viadegradation, e.g., acetoacetamide-N-sulfonic acid (AAA-NSH). Testing foracetoacetamide-N-sulfonic acid content was performed using the HPLCequipment and techniques discussed above. The treatment conditions andresultant impurity contents are shown in Table 2.

TABLE 2 Effects of Temperature and pH on Degradation Products AAA-NSH,wppm, in the int. acesulfame Heating Time, potassium Temp., ° C. min. pHcomposition Example 2 25° C. — 6.5 19 wppm Comp. Ex. B 95° C. 180 min.6.5 33 wppm Comp. Ex. C 95° C. 360 min. 6.5 41 wppm Comp. Ex. C 95° C.180 min. 9.8 89 wppm

As shown in Table 2, the use of high temperature, heating time (whichsimulates residence time), and pH during conventional concentratingoperation conditions results in degradation of acesulfame potassium (oracesulfame-H), which leads to the formation of additional impurities,e.g., acetoacetamide-N-sulfonic acid. By utilizing the concentratingoperation parameters discussed herein, impurities formed via degradationare reduced or eliminated, which leads to higher purity finishedacesulfame potassium compositions, i.e., finished acesulfame potassiumcompositions with low acetoacetamide-N-sulfonic acid content.

While the invention has been described in detail, modifications withinthe spirit and scope of the invention will be readily apparent to thoseof skill in the art. In view of the foregoing discussion, relevantknowledge in the art and references discussed above in connection withthe Background and Detailed Description, the disclosures of which areall incorporated herein by reference. In addition, it should beunderstood that aspects of the invention and portions of variousembodiments and various features recited above and/or in the appendedclaims may be combined or interchanged either in whole or in part. Inthe foregoing descriptions of the various embodiments, those embodimentswhich refer to another embodiment may be appropriately combined withother embodiments as will be appreciated by one of skill in the art.Furthermore, those of ordinary skill in the art will appreciate that theforegoing description is by way of example only, and is not intended tolimit the invention.

We claim:
 1. A process for producing a finished acesulfame potassiumcomposition, the process comprising the steps of: (a) providing a crudeacesulfame potassium composition comprising acesulfame potassium,acetoacetamide and water; (b) concentrating the crude acesulfamepotassium composition to form a water stream and an intermediateacesulfame potassium composition; and (c) separating the intermediateacesulfame potassium composition to form the finished acesulfamepotassium composition comprising acesulfame potassium and less than 33wppm acetoacetamide; wherein the concentrating step (b) is conducted ata temperature below 85° C., and wherein the separating step (c) isconducted at a temperature at or below 20° C.
 2. The process of claim 1,wherein the providing step (a) comprises: reacting sulfamic acid and anamine to form an amidosulfamic acid salt; reacting the amidosulfamicacid salt and acetoacetylating agent to form an acetoacetamide salt;reacting the acetoacetamide salt with cyclizing agent in the cyclizingagent composition to form the cyclic sulfur trioxide adduct; hydrolyzingthe cyclic sulfur trioxide adduct to form an acesulfame-H compositioncomprising acesulfame-H; and neutralizing the acesulfame-H in theacesulfame-H composition to form the crude acesulfame potassiumcomposition.
 3. The process of claim 1, wherein the intermediateacesulfame potassium composition comprises less than 33 wppmacetoacetamide and less than 33 wppm acetoacetamide-N-sulfonic acid. 4.The process of claim 1, wherein the concentrating comprises: evaporatingthe crude acesulfame potassium composition to form the water stream andthe intermediate acesulfame potassium composition comprising acesulfamepotassium and less than 75 wt % water.
 5. The process of claim 4,wherein evaporation residence time is less than 180 minutes.
 6. Theprocess of claim 5, wherein the intermediate acesulfame potassiumcomposition comprises less than 33 wppm acetoacetamide-N-sulfonic acid.7. The process of claim 4, wherein the separating comprises:crystallizing the intermediate acesulfame potassium composition to formacesulfame potassium crystals; and filtering the acesulfame potassiumcrystals to form the finished acesulfame potassium composition.
 8. Theprocess of claim 7, wherein the filtering is conducted at a temperatureat or below 20° C.
 9. The process of claim 7, wherein the crystallizingis conducted at a temperature at or below 20° C.
 10. The process ofclaim 7, wherein the crystallizing is conducted at a pH below
 10. 11.The process of claim 4, wherein the evaporating is conducted at atemperature below 85° C. and the finished acesulfame potassiumcomposition comprises less than 33 wppm acetoacetamide.
 12. The processof claim 11, wherein the intermediate acesulfame potassium compositionfurther comprises from 1 wppb to 33 wppm acetoacetamide and less than 33wppm acetoacetamide-N-sulfonic acid.
 13. The process of claim 4, whereinthe evaporating is conducted at a temperature below 60° C. and theevaporator residence time is less than 50 minutes and the finishedacesulfame potassium composition comprises from 10 wppb to 15 wppmacetoacetamide.
 14. The process of claim 13, wherein the intermediateacesulfame potassium composition comprises from 10 wppb to 25 wppmacetoacetamide and less than 30 wppm acetoacetamide-N-sulfonic acid. 15.The process of claim 4, wherein the evaporating is conducted at atemperature ranging from 20° C. to 55° C., the evaporator residence timeranges from 1 minute to 300 minutes, the separating is conducted at atemperature ranging from −10° C. to 15° C., the separating operationresidence time ranges from 1 to 180 minutes, the finished acesulfamepotassium composition comprises from 10 wppb to 10 wppm acetoacetamide,and from 1 wppb to 20 wppm acetoacetamide-N-sulfonic acid.
 16. Theprocess of claim 7, wherein: (i) the evaporating is conducted at atemperature below 46° C., (ii) the evaporator residence time is lessthan 30 minutes, (iii) crystallizing is conducted at a temperature below20° C. 35° C., and (iv) the finished acesulfame potassium compositioncomprises from 10 wppb to 7 wppm acetoacetamide.
 17. The process ofclaim 16, wherein the intermediate acesulfame potassium compositioncomprises from 10 wppb to 12 wppm acetoacetamide and less than 20 wppmacetoacetamide-N-sulfonic acid.
 18. The process of claim 4, wherein thecrude acesulfame composition further comprises solvent and wherein theprocess further comprises removing solvent from the crude acesulfamepotassium composition prior to the evaporation.
 19. The process of claim4, wherein the weight percentage of acetoacetamide in the finishedacesulfame potassium composition is less than the weight percentage ofacetoacetamide in the crude acesulfame potassium composition.
 20. Theprocess of claim 2, further comprising: separating from the acesulfame-Hcomposition a transition phase comprising at least 2 wt % acetoacetamideto form a purified acesulfame-H composition.
 21. The process of claim20, wherein the neutralizing comprises neutralizing the acesulfame-H inthe purified acesulfame-H composition to form the crude acesulfamepotassium composition.
 22. The process of claim 1, wherein theconcentrating comprises evaporating the crude acesulfame potassiumcomposition to form a water stream and an intermediate acesulfamepotassium composition comprising acesulfame potassium and less than 50wt % water, and the separating comprises crystallizing the intermediateacesulfame potassium composition to form a crystal-containing streamcomprising acesulfame potassium crystals, and filtering thecrystal-containing stream to form the finished acesulfame potassiumcomposition.
 23. The process of claim 22, wherein the filteringcomprises at least two filtration operations.
 24. The process of claim2, wherein the crude acesulfame potassium composition is evaporated toform the water stream and the intermediate acesulfame potassiumcomposition.
 25. The process of claim 24, wherein the intermediateacesulfame potassium composition comprises less than 75 wt % water. 26.The process of claim 24, wherein the crude acesulfame potassiumcomposition is evaporated at a temperature of less than 50° C. and theevaporator residence time is less than 30 minutes.
 27. The process ofclaim 24, wherein the intermediate acesulfame potassium composition iscrystallized to form acesulfame crystals.
 28. The process of claim 27,wherein the intermediate acesulfame potassium composition iscrystallized at a temperature of below 20° C.
 29. The process of claim27, wherein acesulfame crystals are filtered to form the finishedacesulfame composition.
 30. The process of claim 27, wherein acesulfamecrystals are filtered at a temperature below 20° C.
 31. The process ofclaim 1, wherein the finished acesulfame potassium composition comprisesfrom 10 wppb to 15 wppm acetoacetamide.
 32. The process of claim 1,wherein the finished acesulfame potassium composition comprises from 10wppb to 10 wppm acetoacetamide.
 33. The process of claim 1, wherein thefinished acesulfame potassium composition comprises from 10 wppb to 7wppm acetoacetamide.
 34. The process of claim 1, wherein the finishedacesulfame potassium composition comprises less than 33 wppmacetoacetamide-N-sulfonic acid.
 35. The process of claim 1, wherein thefinished acesulfame potassium composition comprises from 1 wppb to 20wppm acetoacetamide-N-sulfonic acid.
 36. The process of claim 1, whereinthe finished acesulfame potassium composition comprises from 10 wppb to10 wppm acetoacetamide and from 1 wppb to 20 wppmacetoacetamide-N-sulfonic acid.
 37. The process of claim 1, wherein thefinished acesulfame potassium composition comprises 0.001 wppm to 5 wppmorganic impurities and/or 0.001 wppm to 5 wppm of at least one heavymetal.
 38. The process of claim 1, wherein the concentrating step (b) isconducted for a residence time of less than 120 minutes.
 39. The processof claim 1, wherein the separating step (c) is conducted for a residencetime of from 10 to 100 minutes.